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0000c2f981838f81c47759242ea123b6121401a9	## Memory Attacks on Device-Independent Quantum Cryptography Jonathan Barrett,[1, 2,][ ∗] Roger Colbeck,[3, 4,][ †] and Adrian Kent[5, 4,][ ‡] 1Department of Computer Science, University of Oxford, Wolfson Building, Parks Road, Oxford OX1 3QD, U.K. 2Department of Mathematics, Royal Holloway, University of London, Egham Hill, Egham, TW20 0EX, U.K. 3Institute for Theoretical Physics, ETH Zurich, 8093 Zurich, Switzerland. 4Perimeter Institute for Theoretical Physics, 31 Caroline Street North, Waterloo, ON N2L 2Y5, Canada. 5Centre for Quantum Information and Foundations, DAMTP, Centre for Mathematical Sciences, University of Cambridge, Wilberforce Road, Cambridge, CB3 0WA, U.K. (Dated: 5[th] August 2013) Device-independent quantum cryptographic schemes aim to guarantee security to users based only on the output statistics of any components used, and without the need to verify their internal functionality. Since this would protect users against untrustworthy or incompetent manufacturers, sabotage or device degradation, this idea has excited much interest, and many device-independent schemes have been proposed. Here we identify a critical weakness of device-independent protocols that rely on public communication between secure laboratories. Untrusted devices may record their inputs and outputs and reveal information about them via publicly discussed outputs during later runs. Reusing devices thus compromises the security of a protocol and risks leaking secret data. Possible defences include securely destroying or isolating used devices. However, these are costly and often impractical. We propose other more practical partial defences as well as a new protocol structure for device-independent quantum key distribution that aims to achieve composable security in the case of two parties using a small number of devices to repeatedly share keys with each another (and no other party). Quantum cryptography aims to exploit the properties of quantum systems to ensure the security of various tasks. The best known example is quantum key distribution (QKD), which can enable two parties to share a secret random string and thus exchange messages secure against eavesdropping, and we mostly focus on this task for concreteness. While all classical key distribution protocols rely for their security on assumed limitations on an eavesdropper’s computational power, the advantage of quantum key distribution protocols (e.g. [1, 2]) is that they are provably secure against an arbitrarily powerful eavesdropper, even in the presence of realistic levels of losses and errors [3]. However, the security proofs require that quantum devices function according to particular specifications. Any deviation – which might arise from a malicious or incompetent manufacturer, or through sabotage or degradation – can introduce exploitable security flaws (see e.g. [4] for practical illustrations). The possibility of quantum devices with deliberately concealed flaws, introduced by an untrustworthy manufacturer or saboteur, is particularly concerning, since (i) it is easy to design quantum devices that appear to be following a secure protocol but are actually completely insecure[1], and (ii) there is no general technique for identifying all possible security loopholes in standard quan [∗Electronic address: jon.barrett@rhul.ac.uk](mailto:jon.barrett@rhul.ac.uk) [†Electronic address: colbeck@phys.ethz.ch](mailto:colbeck@phys.ethz.ch) [‡Electronic address: a.p.a.kent@damtp.cam.ac.uk](mailto:a.p.a.kent@damtp.cam.ac.uk) 1 In BB84 [1], for example, a malicious state creation device could be programmed to secretly send the basis used for the encoding in an additional degree of freedom. tum cryptography devices. This has led to much interest in device-independent quantum protocols, which aim to guarantee security on the fly by testing the device outputs [5–15]: no specification of their internal functionality is required. Known provably secure schemes for deviceindependent quantum key distribution are inefficient, as they require either independent isolated devices for each entangled pair to ensure device-independent security [6, 10–12, 16], or a large number of entangled pairs to generate a short key [6, 16, 17]. Finding an efficient secure device-independent quantum key distribution scheme using two (or few) devices has remained an open theoretical challenge. Nonetheless, in the absence of tight theoretical bounds on the scope for device-independent quantum cryptography, progress to date has encouraged optimism (e.g. [18]) about the prospects for device-independent QKD as a practical technology, as well as for device-independent quantum randomness expansion [13–15] and other applications of device-independent quantum cryptography (e.g. [19]). However, one key question has been generally neglected in work to date on device-independent quantum cryptography, namely what happens if and when devices are reused. Specifically, are device-reusing protocols composable – i.e. do individually secure protocols of this type remain secure when combined? It is clear that reuse of untrusted devices cannot be universally composable, i.e. such devices cannot be securely reused for completely general purposes (in particular, if they have memory, they must be kept secure after the protocol). However, for device-independent quantum cryptography to have significant practical value, one would hope that devices ----- can at least be reused for the same purpose. For example one would like to be able to implement a QKD protocol many times, perhaps with different parties each time, with a guarantee that all the generated keys can be securely used in an arbitrary environment so long as the devices are kept secure. We focus on this type of composability here. We describe a new type of attack that highlights pitfalls in producing protocols that are composable (in the above sense) with device-independent security for reusable devices, and show that for all known protocols such composability fails in the strong sense that purportedly secret data become completely insecure. The leaks do not exploit new side channels (which proficient users are assumed to block), but instead occur through the device choosing its outputs as part of a later protocol. To illustrate this, consider a device-independent scheme that allows two users (Alice and Bob) to generate and share a purportedly secure cryptographic key. A malicious manufacturer (Eve) can design devices so that they record and store all their inputs and outputs. A well designed device-independent protocol can prevent the devices from leaking information about the generated key during that protocol. However, when they are reused, the devices can make their outputs in later runs depend on the inputs and outputs of earlier runs, and, if the protocol requires Alice and Bob to publicly exchange at least some information about these later outputs (as all existing protocols do), this can leak information about the original key to Eve. Moreover, in many existing protocols, such leaks can be surreptitiously hidden in the noise, hence allowing the devices to operate indefinitely like hidden spies, apparently complying with security tests, and producing only data in the form the protocols require, but nonetheless actually eventually leaking all the purportedly secure data. We stress that our results certainly do not imply that quantum key distribution per se is insecure or impractical. In particular, our attacks do not apply to standard QKD protocols in which the devices’ properties are fully trusted, nor if the devices are trusted to be memoryless (but otherwise untrusted), nor necessarily to protocols relying on some other type of partially trusted devices. Our target is the possibility of (full) device-independent quantum cryptographic security, applicable to users who purchase devices from a potentially sophisticated adversarial supplier and rely on no assumption about the devices’ internal workings. The attacks we present raise new issues of composability and point towards the need for new protocol designs. We discuss some countermeasures to our attacks that appear effective in the restricted but relevant scenario where two users only ever use their devices for QKD exchanges with one another, and propose a new type of protocol that aims to achieve security in this scenario while allowing device reuse. Even with these countermeasures, however, we show that security of a key generated with Bob can be compromised if Alice uses the same device for key generation with an additional party. This appears to be a generic problem against which we see no complete defence. Although we focus on device-independent QKD for most of this work, our attacks also apply to other deviceindependent quantum cryptographic tasks. The case of randomness expansion is detailed in Appendix E. Cryptographic scenario.—We use the standard cryptographic scenario for key distribution between Alice and Bob, each of whom has a secure laboratory. These laboratories may be partitioned into secure sub-laboratories, and we assume Alice and Bob can prevent communication between their sub-laboratories as well as between their labs and the outside world, except as authorized by the protocol. The setup of these laboratories is as follows. Each party has a trusted private random string, a trusted classical computer and access to two channels connecting them. The first channel is an insecure quantum channel. Any data sent down this can be intercepted and modified by Eve, who is assumed to know the protocol. The second is an authenticated classical channel which Eve can listen to but cannot impersonate; in efficient QKD protocols this is typically implemented by using some key bits to authenticate communications over a public channel. Each party also uses a sub-laboratory to isolate each of the untrusted devices being used for today’s protocol. They can connect them to the insecure quantum channel, as desired, and this connection can be closed thereafter. They can also interact with each device classically, supplying inputs (chosen using the trusted private string) and receiving outputs, without any other information flowing into or out of the secure sub-laboratory. As mentioned before, existing device-independent QKD protocols that have been proven unconditionally secure [6, 11, 12] require separate devices for each measurement performed by Alice and Bob with no possibility of signalling between these devices[2], or are inefficient [17] (in terms of the amount of key per entangled pair). For practical device-independent QKD, we would like to remove both of these disadvantages and have an efficient scheme needing a small number of devices. Since the protocols in [11, 12] can tolerate reasonable levels of noise and are reasonably efficient, we look first at implementations of protocols taking the form of those in [11, 12], except that Alice and Bob use one measurement device each, i.e., Alice (Bob) uses the same device to perform each of her (his) measurements. We call these two-device protocols (Bob also has a separate isolated source device: see below). The memory of a device can then act as a signal from earlier to later measurements, hence the security proofs of [11, 12] do not apply (see also [20] where a different two-device setup is dis 2 Within the scenario described above, this could be achieved by placing each device in its own sub-laboratory. ----- 1. Entangled quantum states used in the protocol are generated by a device Bob holds (which is separate and kept isolated from his measurement device) and then shared over an insecure quantum channel with Alice’s device. Bob feeds his half of each state to his measurement device. Once the states are received, the quantum channel is closed. 2. Alice and Bob each pick a random input Ai and Bi to their device, ensuring they receive an output bit (Xi and Yi respectively) before making the next input (so that the i-th output cannot depend on future inputs). They repeat this M times. 3. Either Alice or Bob (or both) publicly announces their measurement choices, and the relevant party checks that they had a sufficient number of suitable input combinations for the protocol. If not, they abort. 4. (Sifting.) Some output pairs may be discarded according to some public protocol. 5. (Parameter estimation.) Alice randomly and independently decides whether to announce each remaining bit to Bob, doing so with probability µ (where Mµ ≫ 1). Bob uses the communicated bits and his corresponding outputs to compute some test function, and aborts if it lies outside a desired range. (For example, Bob might compute the CHSH value [21] of the announced data, and abort if it is below 2.5.) 6. (Error correction.) Alice and Bob perform error correction using public discussion, in order to (with high probability) generate identical strings. Eve learns the error correction function Alice applies to her string. 7. (Privacy amplification.) Alice and Bob publicly perform privacy amplification [22], producing a shorter shared string about which Eve has virtually no information. Eve similarly learns the privacy amplification function they apply to their error-corrected strings. TABLE I: Generic structure of the protocols we consider. Although this structure is potentially restrictive, most protocols to date are of this form (we discuss modifications later). Note that we do not need to specify the precise subprotocols used for error correction or privacy amplification. For an additional remark, see Part I of the Appendix cussed). It is an open question whether a secure key can be efficiently generated by a protocol of this type in this scenario. Here we demonstrate that, even if a key can be securely generated, repeat implementations of the protocol using the same devices can render an earlier generated key insecure. Attacks on two-device protocols.—Consider a QKD protocol with the standard structure shown in Table I. We imagine a scenario in which a protocol of this type is run on day 1, generating a secure key for Alice and Bob, while informing Eve of the functions used by Alice for error correction and privacy amplification (for simplicity we assume the protocol has no sifting procedure (Step 4)). The protocol is then rerun on day 2, to generate a second key, using the same devices. Eve can instruct the devices to proceed as follows. On day 1, they follow the protocol honestly. However, they keep hidden records of all the raw bits they generate during the protocol. At the end of day 1, Eve knows the error correction and privacy amplification functions used by Alice and Bob to generate the secure key. On day 2, since Eve has access to the insecure quantum channel over which the new quantum states are distributed, she can surreptitiously modulate these quantum states to carry new classical instructions to the device in Alice’s lab, for example using additional degrees of freedom in the states. These instructions tell the device the error correction and privacy amplification functions used on day 1, allowing it to compute the secret key generated on day 1. They also tell the device to deviate from the honest protocol for randomly selected inputs, by producing as outputs specified bits from this secret key. (For example, “for input 17, give day 1’s key bit 5 as output”.) If any of these selected outputs are among those announced in Step 5, Eve learns the corresponding bits of day 1’s secret key. We call this type of attack, in which Eve attempts to gain information from the classical messages sent in Step 5, a parameter estimation attack. If she follows this cheating strategy for Nµ[−][1] < M input bits, Eve is likely to learn roughly N bits of day 1’s secret key. Moreover, only the roughly N output pairs from this set that are publicly compared give Alice and Bob statistical information about Eve’s cheating. Alice and Bob cannot a priori identify these cheating output pairs among the ≈ µM they compare. Thus, if the tolerable noise level is comparable to Nµ[−][1]M [−][1], Eve can (with high probability) mask her cheating as noise. (Note that in unconditional security proofs it is generally assumed that eavesdropping is the cause of all noise. Even if in practice Eve cannot reduce the noise to zero, she can supply less noisy components than she claims and use the extra tolerable noise to cheat). In addition, Alice and Bob’s devices each separately have the power to cause the protocol to abort on any day of their choice. Thus – if she is willing to wait long enough – Eve can program them to communicate some or all information about their day 1 key, for instance by encoding the relevant bits as a binary integer N = b1 . . . bm and choosing to abort on day (N + 2)[3]. We call this type of attack an abort attack. Note that it cannot be detected until it is too late. As mentioned above, some well known protocols use many independent and isolated measurement devices. These protocols are also vulnerable to memory attacks, as explained in Appendix D. 3 In practice, Eve might infer a day (N +2) abort from the fact that Alice and Bob have no secret key available on day (N +2), which in many scenarios might detectably affect their behaviour then or subsequently. Note too that she might alternatively program the devices to abort on every day from (N + 2) onwards if this made N more easily inferable in practice. ----- Modified protocols.—We now discuss ways in which these attacks can be partly defended against. Countermeasure 1.—All quantum data and all public communication of output data in the protocol come from one party, say Bob. Thus, the entangled states used in the protocol are generated by a separate isolated device held by Bob (as in the protocol in Table 1) and Bob (rather than Alice) sends selected output data over a public channel in Step 5. If Bob’s device is forever kept isolated from incoming communication, Eve has no way of sending it instructions to calculate and leak secret key bits from day 1 (or any later day). Existing protocols modified in this way are still insecure if reused, however. For example, in a modified parameter estimation attack, Eve can pre-program Bob’s device to leak raw key data from day 1 via output data on subsequent days, at a low enough rate (compared to the background noise level) that this cheating is unlikely to be detected. If the actual noise level is lower than the level tolerated in the protocol, and Eve knows both (a possibility Alice and Bob must allow for), she can thereby eventually obtain all Bob’s raw key data from day 1, and hence the secret key. In addition, Eve can still communicate with Alice’s device, and Alice needs to be able to make some public communication to Bob, if only to abort the protocol. Eve can thus obtain secret key bits from day 1 on a later day using an abort attack. Countermeasure 2. [23] —Encrypt the parameter estimation information sent in Step 5 with some initial preshared seed randomness. Provided the seed required is small compared to the size of final string generated (which is the case in efficient QKD protocols [11, 12]), the protocol then performs key expansion[4]. Furthermore, even if they have insufficient initial shared key to encrypt the parameter estimation information, Alice and Bob could communicate the parameter estimation information unencrypted on day 1, but encrypt it on subsequent days using generated key. Note that this countermeasure is not effective against abort attacks, which can now be used to convey all or part of their day 1 raw key. This type of attack seems unavoidable in any standard cryptographic model requiring composability and allowing arbitrarily many device reuses if either Alice or Bob has only a single measurement device. This countermeasure is also not effective in general cryptographic environments involving communication with multiple users who may not all be trustworthy. Suppose that Alice wants to share key with Bob on day 1, but with Charlie on day 2. If Charlie becomes corrupted by Eve, then, for example by hiding data in 4 QKD is often referred to as quantum key expansion in any case, taking into account that a common method of authenticating the classical channel uses pre-shared randomness. the parameter estimation, Eve can learn about day 1’s key (we call this an impostor attack ). This attack applies in many scenarios in which users might wish to use device-independent QKD. For example, suppose Alice is a merchant and Bob is a customer who needs to communicate his credit card number to Alice via QKD to complete the sale. The next day, Eve can pose as a customer, carry out her own QKD exchange with Alice, and extract information about Bob’s card number without being detected. Countermeasure 3.—Alternative protocols using additional measurement devices. Suppose Alice and Bob each have m measurement devices, for some small integer m ≥ 2. They perform Steps 1–6 of a protocol that takes the form given in Table I but with Countermeasures 1 and 2 applied. They repeat these steps for each of their devices in turn, ensuring no communication between any of them (i.e., they place each in its own sub-laboratory). This yields m error-corrected strings. Alice and Bob concatenate their strings before performing privacy amplification as in Step 7. However, they further shorten the final string such that it would (with near certainty) remain secure if one of the m error-corrected strings were to become known to Eve through an abort attack. (See Table 2, and Appendix C for more details). This countermeasure doesn’t avoid impostor attacks. Instead, the idea is to prevent useful abort attacks (as well as parameter estimation attacks due to Countermeasure 2), and hence give us a secure and composable protocol, provided the keys produced on successive days are always between the same two users. The information each device has about day 1’s key is limited to the raw key it produced. Thus, if each device is programmed to abort on a particular day that encodes their day 1 raw key, after an abort, Eve knows one of the devices’ raw keys and has some information on the others (since she can exclude certain possibilities based on the lack of abort by those devices so far). After an abort, Alice and Bob should cease to use any of their devices unless and until such time that they no longer require that their keys remain secret. Intuitively, provided the set of m keys was sufficiently shortened in the privacy amplification step, Eve has essentially no information about the day 1 secret key, which thus (we conjecture) remains secure. Countermeasure 4.—Alice and Bob share a small initial secret key and use part of it to choose the privacy amplification function in Step 7 of the protocol, which may then never become known to Eve. Even in this case, Eve can pre-program Bob’s measurement device to leak raw data from day 1 on subsequent days, either via a parameter estimation attack or via an abort attack. While Eve cannot obtain bits of the secret key so directly in this case, provided the protocol is composed sufficiently many times, she can eventually obtain all the raw key. This means that Alice and Bob’s residual security ultimately derives only from the initial shared secret key: their QKD protocol produces no extra permanently secure data. ----- In summary, we have shown how a malicious manufacturer who wishes to mislead users or obtain data from them can equip devices with a memory and use it in programming them. The full scope of this threat seems to have been overlooked in the literature on deviceindependent quantum cryptography to date. A task is potentially vulnerable to our attacks if it involves secret data generated by devices and if Eve can learn some function of the device outputs in a subsequent protocol. Since even causing a protocol to abort communicates some information to Eve, the class of tasks potentially affected is large indeed. In particular, for one of the most important applications, QKD, none of the protocols so far proposed remain composably secure in the case that the devices are supplied by a malicious adversary. One can think of the problems our attacks raise as a new issue of cryptographic composability. One way of thinking of standard composability is that a secure output from a protocol must still have all the properties of an ideal secure output when combined with other outputs from the same or other protocols. The deviceindependent key distribution protocols we have examined fail this test because the reuse of devices can cause later outputs to depend on earlier ones. In a sense, the underlying problem is that the usage of devices is not composably secure. This applies too, of course, for devices used in different protocols: devices used for secure randomness expansion cannot then securely be used for key distribution without potentially compromising the generated randomness, for example. It is worth reiterating that our attacks do not apply against protocols where the devices are trusted to be memoryless. Indeed, there are schemes that are composably secure for memoryless devices [11, 12]. We also stress that our attacks do not apply to all protocols for device-independent quantum tasks related to cryptography. For example, even devices with memories cannot mimic nonlocal correlations in the absence of shared entanglement [24, 25]. In addition, in applications that require only short-lived secrets, devices may be reused once such secrets are no longer required. Partially secure device-independent protocols for bit commitment and coin tossing [19], in which the committer supplies devices to the recipient, are also immune from our attacks, so long as the only data entering the devices come from the committer. Note too that, in practice the number of uses required to apply the attacks may be very large, for example, in the case of some of the abort attacks we described. One can imagine a scenario in which Alice and Bob want to carry out device-independent QKD no more than n times for some fixed number n, each is confident in the other’s trustworthiness throughout, the devices are used for no other purpose and are destroyed after n rounds, and key generation is suspended and the devices destroyed if a single abort occurs. If the only relevant information con veyed to Eve is that an abort occurs on one of the n days, she can only learn at most log n bits of information about the raw key via an abort attack. Hence one idea is that, using suitable additional privacy amplification, Alice and Bob could produce a device-independent protocol using two measurement devices that is provably secure when restricted to no more than n bilateral uses. It would be interesting to analyse this possibility, which, along with the protocol presented in Table 2, leads us to hold out the hope of useful security for fully device-independent QKD, albeit in restricted scenarios. We have also discussed some possible defences and countermeasures against our attacks. A theoretically simple one is to dispose of – i.e. securely destroy or isolate – untrusted devices after a single use (see Appendix B). While this would restore universal composability, it is clearly costly and would severely limit the practicality of device-independent quantum cryptography. Another interesting possibility is to design protocols for composable device-independent QKD guaranteed secure in more restricted scenarios. However, the impostor attacks described above appear to exclude the possibility of composably secure device-independent QKD when the devices are used to exchange key with several parties. Many interesting questions remain open. Nonetheless, the attacks we have described merit a serious reappraisal of current protocol designs and, in our view, of the practical scope of universally composable quantum cryptography using completely untrusted devices. Added Remark: Since the first version of this paper, there has been new work in this area that, in part, explores countermeasure 2 in more detail [26]. In addition, two new works on device-independent QKD with only two devices have appeared [27, 28]. Note that these do not evade the attacks we present, but apply to the scenario where used devices are discarded. Acknowledgements.—We thank Anthony Leverrier and Gonzalo de la Torre for [23], Llu´ıs Masanes, Serge Massar and Stefano Pironio for helpful comments. JB was supported by the EPSRC, and the CHIST-ERA DIQIP project. RC acknowledges support from the Swiss National Science Foundation (grants PP00P2-128455 and 20CH21-138799) and the National Centre of Competence in Research ‘Quantum Science and Technology’. AK was partially supported by a Leverhulme Research Fellowship, a grant from the John Templeton Foundation, and the EU Quantum Computer Science project (contract 255961). This research is supported in part by Perimeter Institute for Theoretical Physics. Research at Perimeter Institute is supported by the Government of Canada through Industry Canada and by the Province of Ontario through the Ministry of Research and Innovation. ----- [1] Bennett, C. H. & Brassard, G. Quantum cryptography: Public key distribution and coin tossing. In Proceedings of IEEE International Conference on Computers, Systems, and Signal Processing, 175–179. IEEE (New York, 1984). [2] Ekert, A. K. Quantum cryptography based on Bell’s theorem. 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IEEE Transactions on information theory 56, 4674–4681 (2010). [35] Fehr, S., Gelles, R. & Schaffner, C. Security and composability of randomness expansion from Bell inequalities. [e-print arXiv:1111.6052 (2011).](arXiv:1111.6052) [36] Vazirani, U. & Vidick, T. Certifiable quantum dice or, testable exponential randomness expansion. e-print [arXiv:1111.6054 (2011).](arXiv:1111.6054) [37] Pironio, S. & Massar, S. Device-independent randomness expansion secure against quantum adversaries. e-print [arXiv:1111.6056 (2011).](arXiv:1111.6056) Appendix A: Separation of sources and measurement devices We add here one important comment about the general structure of the generic protocol given in Table 1 of the main text. There it was crucial that in Step 1, in the ----- case where Bob (rather than Eve) supplies the states, he does so using a device that is isolated from his measurement device. If, on the other hand, Bob had only a single device that both supplies states and performs measurements, then his device can hide information about day 1’s raw key in the states he sends on day 2. (This can be done using states of the form specified in the protocol, masking the errors as noise as above. Alternatively, the data could be encoded in the timings of the signals or in quantum degrees of freedom not used in the protocol.) Appendix B: Toxic device disposal As noted in the main text, standard cryptographic models postulate that the parties can create secure laboratories, within which all operations are shielded from eavesdropping. Device-independent quantum cryptographic models also necessarily assume that devices within these laboratories cannot signal to the outside – otherwise security is clearly impossible. Multi-device protocols assume that the laboratories can be divided into effectively isolated sub-laboratories, and that devices in separate sub-laboratories cannot communicate. In other words, Alice and Bob must be able to build arbitrary configurations of screening walls, which prevent communication among Eve and any of her devices, and allow only communications specified by Alice and Bob. Given this, there is no problem in principle in defining protocols which prescribe that devices must be permanently isolated: the devices simply need to be left indefinitely in a screened sub-laboratory. While this could be detached from the main working laboratory, it must be protected indefinitely: screening wall material and secure space thus become consumed resources. And indeed in some situations, it may be more efficient to isolate devices, rather than securely destroy them, since devices can be reused once the secrets they know have become public by other means. For example, one may wish to securely communicate the result of an election before announcing it, but once it is public, the devices used for this secure communication could be safely reused. The alternative, securely destroying devices and then eliminating them from the laboratory, preserves laboratory space but raises new security issues: consider, for example, the problems in disposing of a device programmed to change its chemical composition depending on its output bit. That said, no doubt there are pretty secure ways of destroying devices, and no doubt devices could be securely isolated for long periods. However, the costs and problems involved, together with the costs of renewing devices, make us query whether these are really viable paths for practical device-independent quantum cryptography. Appendix C: Privacy Amplification Here we briefly outline the important features of privacy amplification, which is a key step in the protocol. As explained in the main text, the idea is to compress the string such that (with high probability) an eavesdropper’s knowledge is reduced to nearly zero. This usually works as follows. Suppose Alice and Bob share some random string, X, which may be correlated with a quantum system, E, held by the eavesdropper. Alice also holds some private randomness, R. The state held by Alice and Eve then takes the form � ρXRE = PX (x)PR(r)\|x⟩⟨x\|X ⊗\|r⟩⟨r\|R ⊗ ρ[x]E[,] x,r where {ρ[x]E[}][x][ are normalized density operators, and] PR(r) = 1/\|R\|. The randomness R is used to choose a function fR ∈F, where F is some suitably chosen set, to apply to X such that, even if she learns R, the eavesdropper’s knowledge about the final string is close to zero. If we call the final string S = fR(X), then Eve has no knowledge about it if the final state takes the form τS ⊗ ρRE, where τS is maximally mixed on S. However, we cannot usually attain such a state, and instead measure the success of a protocol by its variation from this ideal, measured using the trace distance, D. Denoting the final state (after applying the function) by ρSRE, we are interested in D(ρSRE, τS ⊗ ρRE). Fortunately, several sets of function are known for which the above distance can be made arbitrarily small. Two common constructions are those based on twouniversal hash functions [3, 29–31] and Trevisan’s extractor [32, 33]. The precise details of these is not very important for the present work (we refer the interested reader to the references), nor is it important which we choose. However, it is worth noting that for two-universal hash functions, the size of the seed needs to be roughly equal to that of the final string, while for Trevisan’s extractor, this can be reduced to roughly the logarithm of the length of the initial string (in the latter case, this may allow it to be sent privately, if desired). For both, the amount that the string should be compressed is quantified by the smooth conditional minentropy, which we now define. For a state ρAB, the nonsmooth conditional min-entropy is defined as Hmin(A\|B)ρ := max σB [sup][{][λ][ ∈] [R][ : 2][−][λ][1][1][A][ ⊗] [σ][B][ ≥] [ρ][AB][}][,] in terms of which the smooth min entropy is given by Hmin[ε] [(][A][\|][B][)][ρ][ := max]ρ¯AB [H][min][(][A][\|][B][)][ρ][¯][.] The maximization over ¯ρ is over a set of states that are close to ρAB according to some distance measure (see, for example, [34] for a discussion). The significance for privacy amplification can be seen as follows. In [3], it is shown that if f is chosen randomly from a set of two-universal hash functions, and applied ----- 1. Entangled quantum states used in the protocol are generated by a device Bob holds (which is separate and kept isolated from his measurement devices) and then shared over an insecure quantum channel with Alice’s first device. Bob feeds his half of each state to his first measurement device. Once the states are received, the quantum channel is closed. 2. Alice and Bob each pick a random input Ai and Bi to their first device, ensuring they receive an output bit (Xi and Yi respectively) before making the next input (so that the i-th output cannot depend on future inputs). They repeat this M times. 3. Bob publicly announces his measurement choices, and Alice checks that for a sufficient number of suitable input combinations for the protocol. If not, Alice aborts. 4. (Sifting.) Some output pairs may be discarded according to some protocol. 5. (Parameter estimation.) Alice and Bob use their preshared key to randomly select some output pairs (they select only a small fraction, hence the amount of key required for this is small). For each of the selected pairs, Bob encrypts his output and sends it to Alice. Alice uses the communicated bits and her corresponding outputs to compute some test function, and aborts if it lies outside a desired range. 6. (Error correction.) Alice and Bob perform error correction using public discussion, in order to (with high probability) generate identical strings. Eve learns the error correction function Alice applies to her string. 7. Alice and Bob repeat Steps 1–6 for each of their m devices (ensuring the devices cannot communicate throughout) 8. (Privacy amplification.) Alice and Bob concatenate their m strings and publicly perform privacy amplification [22], producing a shorter shared string about which Eve has virtually no information. In this step, the size of their final string is chosen such that (with high probability) it will remain secure even if one of the raw strings or its error corrected version becomes known. TABLE 2: Structure of the protocol from the main text with modifications as in Countermeasure 3. For this protocol Alice and Bob each have m ≥ 2 measurement devices, and Bob has one device for creating states. They are all kept isolated from one another. to the raw string X, as above, then for \|S\| = 2[t] and any ε ≥ 0, D(ρSRE, τS ⊗ ρRE) ≤ ε + [1] 2 [(][H]min[ε] [(][X][\|][E][)][−][t][)]. 2 [2][−] [1] (An analogous statement can be made for Trevisan’s extractor [33].) Thus, if Alice compresses her string to length t = Hmin[ε] [(][X][\|][E][)][ −] [ℓ][, then the final state after ap-] plying the hash function has distance ε + [1]2 [2][−][ℓ/][2][ to a] state about which Eve has no knowledge. Turning to the QKD protocol in Table 1 of the main text, in the case of hashing the privacy amplification procedure consists of Alice selecting t depending on the test function computed in the parameter estimation step. She then uses local randomness to choose a hash function to apply to her string, and announces this to Bob, who applies the same function to his string (since we have already performed error correction, this string should be identical to Alice’s). The idea is that, if t is chosen appropriately, it is virtually impossible that the parameter estimation tests pass and the final state at the end of the protocol is not close to one for which Eve has no knowledge about the final string. In the modified protocol in Table 2, we expect each pair of devices to contribute roughly the same amount of smooth min entropy to the concatenated string. Thus, since there are m devices, in order to tolerate the potential revelation of one of the error-corrected strings through an abort attack, Alice should choose t to be roughly (m − 1)/m shorter than she would otherwise. Appendix D: Memory attacks on multi-device QKD protocols To illustrate further the generality of our attacks, we now turn to multi-device protocols, and show how to break iterated versions of two well known protocols. Attacks on compositions of the BHK protocol The Barrett-Hardy-Kent (BHK) protocol [6] requires Alice and Bob to share MN [2] pairs of systems (where M and N are both large with M ≪ N ), in such a way that no measurements on any subset can effectively signal to the others. In a device-independent scenario, we can think of these as black box devices supplied by Eve, containing states also supplied by Eve. Each device is isolated within its own sub-laboratory of Alice’s and Bob’s, so that Alice and Bob have MN [2] secure sublaboratories each. The devices accept integer inputs in the range {0, . . ., N − 1} and produce integer outputs in the range {0, 1}. Alice and Bob choose random independent inputs, which they make public after obtaining all the outputs. They also publicly compare all their outputs except for those corresponding to one pair randomly chosen from among those in which the inputs differ by ±1 or 0 modulo N . If the publicly declared outputs agree with quantum statistics for specified measurement basis choices (corresponding to the inputs) on a singlet state, then they accept the protocol as secure, and take the final undeclared outputs (which are almost certainly anticorrelated) to define their shared secret bit. The BHK protocol produces (with high probability) precisely one secret bit: evidently, it is extremely inefficient in terms of the number of devices required. It also requires essentially noise-free channels and errorfree measurements. Despite these impracticalities it il ----- lustrates our theoretical point well. Suppose that Alice and Bob successfully complete a run of the BHK protocol and then (unauthorised by BHK) decide to use the same 2MN [2] devices to generate a second secret bit, and ask Eve to supply a second batch of states to allow them to do this. Eve — aware in advance that the devices may be reused — can design them to function as follows. In the first run of the protocol, she supplies a singlet pair to each pair of devices and the devices function honestly, carrying out the appropriate quantum measurements on their singlets and reporting the outcomes as their outputs. However, they also store in memory their inputs and outputs. In the second run, Eve supplies a fresh batch of singlet pairs. However, she also supplies a hidden classical signal identifying the particular pair of devices that generated the first secret bit. (This signal need go to just one of this pair of devices, and no others.) On the second run, the identified device produces as output the same output that it produced on the first run (i.e. the secret bit generated, up to a sign convention known to Eve). All other devices function honestly on the second run. With probability [MN]MN[ 2][−][2][, the output from the cheating][1] device on the second run will be made public, thus revealing the first secret bit to Eve. Moreover, with probability 1 − 23N [+][ O][(][N][ −][2][), this cheating will not be detected by] Alice and Bob’s tests, so that Eve learns the first secret bit without her cheating even being noticed. There are defences against this specific attack. First, the BHK protocol [6] can be modified so that only outputs corresponding to inputs differing by ±1 or 0 are publicly shared.[5] While this causes Eve to wait many rounds for the secret bit to be leaked, and increases the risk her cheating will be detected, it leaves the iterated protocol insecure. Second, Alice and Bob could securely destroy or isolate the devices producing the secret key bit outputs, and reuse all their other devices in a second implementation. Since only the devices generating the secret key bit have information about it, this prevents it from being later leaked. While effective, this last defence really reflects the inefficiency of the BHK protocol: to illustrate this, we turn next to a more efficient multi-device protocol. Attacks on compositions of the HR protocol H¨anggi and Renner (HR) [11] consider a multi-device QKD protocol related to the Ekert [2] protocol, in which Alice and Bob randomly and independently choose one of 5 As originally presented, the BHK protocol requires public exchange of all outputs except those defining the secret key bit. This is unnecessary, and makes iterated implementations much more vulnerable to the attacks discussed here. two or three inputs respectively for each of their devices. If the devices are functioning honestly, these correspond to measurements of a shared singlet in the bases U0, U1 (Alice) and V0, V1, V2 (Bob), defined by the following vectors and their orthogonal complements U1 ↔\|0⟩, V0 ↔ cos(π/8)\|0⟩ + sin(π/8)\|1⟩, U0, V2 ↔ cos(π/4)\|0⟩ + sin(π/4)\|1⟩, V1 ↔ cos(3π/8)\|0⟩ + sin(3π/8)\|1⟩ . The raw key on any given run is defined by the ≈ 1/6 of the cases in which U0 and V2 are chosen. Information reconciliation and privacy amplification proceed according to protocols of the type described in the main text (in which the functions used are released publicly). Evidently, our attacks apply here too if (unauthorised by HR) the devices are reused to generate further secret keys. Eve can identify the devices that generate the raw key on day 1, and request them to release their key as cheating outputs on later days, gradually enough that the cheating will be lost in the noise. Since the information reconciliation and privacy amplification functions were made public by Alice, she can then obtain the secret key. Even if she is unable to communicate directly with the devices for a long time (because they were pre-installed with a very large reservoir of singlets), she can program all devices to gradually release their day 1 outputs over subsequent days, and so can still deduce the raw and secret keys. Alice and Bob could counter these attacks by securely destroying or isolating all the devices that generated raw key on day 1 — but this costs them 1/6 of their devices, and they have to apply this strategy each time they generate a key, leaving (5/6)[N] of the devices after N runs, and leaving them able to generate shorter and shorter keys. As the length of secure key generated scales by (5/6)[N] (or worse, allowing for fluctuations due to noise) on each run, the total secret key generated is bounded by ≈ 6M, where M is the secret key length generated on day 1. Note that, as in the case of the iterated BHK protocol, all devices that generate secret key become toxic and cannot be reused. While the relative efficiency of the HR protocol ensures a (much) faster secret key rate, it also requires an equally fast device depletion rate. This example shows that our attacks pose a generic problem for device-independent QKD protocols of the types considered to date. Appendix E: Device-independent randomness expansion protocols: attacks and defences Device-independent quantum randomness expansion (DVI QRE) protocols were introduced by two of us [13, 15], developed further by [14, 35–37], and there now exist schemes with unconditional security proofs [36]. The ----- cryptographic scenario here is slightly different from that of key distribution in that there is only one honest party, Alice. Alice’s aim is to expand an initial secret random string to a longer one that is guaranteed secret from an eavesdropper, Eve, even if the quantum devices and states used are supplied by Eve. The essential idea is that seed randomness can be used to carry out nonlocality tests on the devices and states, within one or more secure laboratories, in a way that guarantees (with numerical bounds) that the outcomes generate a partially secret and random string. Privacy amplification can then be used to generate an essentially fully secret random string, which (provided the tests are passed) is significantly longer than the initial seed. There are already known pitfalls in designing such protocols. For example, although one might think that carrying out a protocol in a single secure laboratory guarantees that the initially secure seed string remains secure, and so guarantees randomness expansion if any new secret random data is generated, this is not the case [15]. Eve’s devices may be programmed to produce outputs depending on the random seed in such a way that the length of the final secret random string depends on the initial seed. Protocols with this vulnerability are not composably secure. (To see this can be a practical problem, note that Eve may infer the length of the generated secret random string from its use.) A corollary of our results is that, if one wants to reuse the devices to generate further randomness, it is crucial to carry out DVI QRE protocols with devices permanently held within a single secure laboratory, avoiding any public communication of device output data at any stage. It is crucial too that the devices themselves are securely isolated from classical communications and computations within the laboratory, to prevent them from learning details of the reconciliation and privacy amplification. Even under these stringent conditions, our attacks still apply in principle. For example, consider a noise-tolerant protocol that produces a secret random output string of variable length, depending on the values of test functions of the device outputs (the analogue of QKD parameter estimation for QRE) that measure how far the device outputs deviate from ideal honest outputs. This might seem natural for any single run, since – if the devices are never reused – the length of the provably secret random string that can be generated does indeed depend on the value of a suitable test function. However, iterating such a protocol allows the devices to leak information about (at least) their raw outputs on the first run by generating artificial noise in later rounds, with the level of extra noise chosen to depend suitably on the output values. Such noise statistically affects the length of the output random strings on later rounds. In this way, suitably programmed devices could ultimately allow Eve to infer all the raw outputs from the first round, given observation of the key string lengths created in later rounds. This makes the round one QRE insecure, since given the raw outputs for round one, and knowing the protocol, Eve knows all information about the output random string for round one, except that determined by the secret random seed. One defence against this would be to fix a length L for the random string generated corresponding to a maximum acceptable noise level, and then to employ the Procrustean tactic of always reducing the string generated to length L, regardless of the measured noise level. Even then, though, unless some restriction is placed on the number of uses, the abort attack on QKD protocols described in the main text also applies here. The devices have the power to cause the protocol to abort on any round of their choice, and so – if she is willing to wait long enough – Eve can program them to communicate any or all information about their round 1 raw outputs by choosing the round on which they cause an abort. We also described in the main text a moderately costly but apparently effective defence against abort attacks on QKD protocols, in which Alice and Bob each have several isolated devices that independently generate raw sub-keys, which are concatenated and privacy amplified so that exposing a single sub-key does not significantly compromise the final secret key. This defence appears equally effective against abort attacks on deviceindependent quantum randomness expansion protocols. Since quantum randomness expansion generally involves only a single party, these protocols are not vulnerable to the impostor attacks described in the main text. It thus appears that it may be possible in principle to completely defend them against memory attacks, albeit at some cost. It is also worth noting that there are many scenarios in which one only needs short-lived randomness, for example, in many gambling applications, bets are often placed about random data that are later made public. In such scenarios, once such random data have been revealed, the devices could be reused without our attacks presenting any problem. -----	Memory attacks on device-independent quantum cryptography.	Device-independent quantum cryptographic schemes aim to guarantee security to users based only on the output statistics of any components used, and without the need to verify their internal functionality. Since this would protect users against untrustworthy or incompetent manufacturers, sabotage, or device degradation, this idea has excited much interest, and many device-independent schemes have been proposed. Here we identify a critical weakness of device-independent protocols that rely on public communication between secure laboratories. Untrusted devices may record their inputs and outputs and reveal information about them via publicly discussed outputs during later runs. Reusing devices thus compromises the security of a protocol and risks leaking secret data. Possible defenses include securely destroying or isolating used devices. However, these are costly and often impractical. We propose other more practical partial defenses as well as a new protocol structure for device-independent quantum key distribution that aims to achieve composable security in the case of two parties using a small number of devices to repeatedly share keys with each other (and no other party).	2012.0	2012-01-20 00:00:00	https://www.semanticscholar.org/paper/0000c2f981838f81c47759242ea123b6121401a9	Physical Review Letters	True
0002c60ed10a8868930b8f971af29e62b498f6b8	OBSERVARE Universidade Autónoma de Lisboa e-ISSN: 1647-7251 Vol. 14, Nº. 1 (May-October 2023) # NOTES AND REFLECTIONS PROBLEMS OF EVALUATION OF DIGITAL EVIDENCE BASED ON BLOCKCHAIN TECHNOLOGIES[1] OTABEK PIRMATOV [pirmatov.otabek.89@inbox.ru](mailto:pirmatov.otabek.89@inbox.ru) Assistant Professor of the Department of Civil Procedural and Economic Procedural Law, Tashkent State University of Law (Uzbekistan), Doctor of Philosophy in Law (PhD) ## Introduction Digital evidence is fundamentally different from physical evidence and written evidence. Securing physical evidence is primarily to prevent it from being lost or difficult to obtain in the future. Compared to traditional evidence, electronic evidence is fragile, easy to change and delete, and difficult to guarantee its authenticity. For example, data on a personal computer may be lost due to misuse, virus attack, etc. During the preparation of the case, the video can be deleted in order to hide the facts. In fact, most electronic evidence is stored in a central database. If the database is unreliable, the validity of the data is not guaranteed. Obviously, how to ensure the authenticity and integrity of digital evidence is very important when storing it. Because digital evidence is created by special high-tech, it is easier to change it in practice. More attention should be paid to its authenticity. Digital evidence is more likely to be tampered with in practice. The main methods of digital evidence storage (pre-trial provision) in civil court proceedings are as follows: 1) sealing or closing the means of keeping the original of evidence; 2) printing, photographing and sound or visual recording; 1 This text is devoted the issues of evaluation of digital evidence based on blockchain technologies in civil court proceedings. The article states that since it is not possible to change and delete evidence based on block-chain technology, contracts based on blockchain technology and documents issued by government bodies are considered acceptable evidence by the courts. It is highlighted that the usage of evidence based on block-chain technology in conducting civil court cases will prevent the need for notarization of digital evidence by the parties in the future. ----- JANUS.NET, e journal of International Relations e-ISSN: 1647-7251 Vol. 14, Nº. 1 (May-October 2023), pp. 279-288 _Notes and Reflections_ _Problems of evaluation of digital evidence based on blockchain technologies_ Otabek Pirmatov 3) drawing up reports; 4) authentication; 5) provision through a notary office; 6) storage through block-chain; 7) casting a time stamp (time stamp). Block-chain is a database where data is securely stored. This is achieved by connecting each new record with the previous one, resulting in a chain consisting of data blocks ("block chain" in English)—hence the name. Physically, the blockchain database is distributed, allowing authorized users to independently add data. It is impossible to make changes to previously stored data, as this action will break the chain, and it is "immutability" that makes the block-chain a safe and reliable means of storing digital records in public databases[2]. Officially, the history of “blocks and chains” begins on October 31, 2008, when someone under the pseudonym Satoshi Nakamoto mentioned the blockchain in a white paper (base document) about the network of the first cryptocurrency - bitcoin. The fundamental principles for applying decentralization and immutability to document accounting were laid down as early as the 1960s and 1970s, but the closest to them are the works of scientists Stuart Haber and W. Scott Stornett, who in 1991 described a scheme for sequentially creating blocks in which a hash is located. The technology was even patented, but for its time it became a Da Vinci helicopter - there was no technical possibility to implement the idea, and interest in it disappeared. The patent expired in 2004, just four years before Satoshi and his white paper appeared[3]. ## 1. Literature review S.S. Gulyamov defines block-chain as follows: blockchain (chain of blocks) is a distributed set of data, in which data storage devices are not connected to a common server. These data sets are called blocks and are stored in an ever-growing list of ordered records. Each block will have a timestamp and a reference to the previous block. The use of encryption ensures that users cannot write to the file without them, while the presence of private keys can only modify a certain part of the blockchains. In addition, encryption ensures synchronization of all users' copies of the distributed chain of blocks (Gulyamov, 2019: 114). Primavera De Filippi and Aaron Wright (2018) point out that block-chain technology is different from other electronic evidence because it cannot be forgotten. The technology itself has evidential value for the judicial system. _Markus Kaulartz, Jonas Gross, Constantin Lichti, Philipp Sandner_ define block-chain technology is getting increasingly renowned, as more and more companies develop blockchain-based prototypes, e.g., in the context of payments, digital identities, and the 2 [https://www.gazeta.uz/uz/2022/08/26/blockchain-technology/](https://www.gazeta.uz/uz/2022/08/26/blockchain-technology/) 3 [https://www.forbes.ru/mneniya/456381-cto-takoe-blokcejn-vse-cto-nuzno-znat-o-tehnologii](https://www.forbes.ru/mneniya/456381-cto-takoe-blokcejn-vse-cto-nuzno-znat-o-tehnologii) ----- JANUS.NET, e journal of International Relations e-ISSN: 1647-7251 Vol. 14, Nº. 1 (May-October 2023), pp. 279-288 _Notes and Reflections_ _Problems of evaluation of digital evidence based on blockchain technologies_ Otabek Pirmatov supply chain. One use case of blockchain is often seen in the tamper-proof storage of information and documentation of facts. This is due to the fact that records on a blockchain are “practically resistant” to manipulation as a consequence of the underlying cryptography and the consensus mechanism. If a block-chain is used for storing information, the question arises whether the data stored on a block-chain can be used as evidence in court. In the following article, we will analyze this question[4]. According to Alexey Sereda, the correct usage of blockchain technologies will eliminate the need for lawyers to perform certain mechanical tasks to a significant extent: checking counterparties, contacting other experts (bodies), the need for notarization, etc. All this allows lawyers to focus their efforts on solving other more important tasks[5]. Vivien Chan and Anna Mae Koo define blockchain is a decentralized and open distributed ledger technology. Electronic data (e.g. in a transaction on an e-shopping platform, the transaction time, purchase amount, currency and participants, etc.) will be uploaded to a network of computers in “blocks”. Since the data saved in a blockchain is stored in a network of computers in a specific form and is publicly available for anyone to view, the data is irreversible and difficult to be manipulated. Anyone who has handled an online infringement case knows the race against time in preserving evidence. However, screenshots saved in PDF formats are easy to be tampered with and are of scant probative value before the Chinese courts, unless notarized. Making an appointment with, and appearing before a notary is another timeconsuming and expensive process. With blockchain, these procedures can be simplified and improved in the following ways: 1. E-evidence can be saved as blockchain online instantaneously without a notary public; 2. Cost for generating blockchain evidence is lower than traditional notarization; 3. Admissibility of block-chain evidence has been confirmed by statute and many courts in China because of the tamper-free nature of block-chain technology; 4. Possible combination of online monitoring and evidence collection process: with blockchain technology and collaboration with different prominent online platforms (e.g. Weixin), it is possible to automate online monitoring of your intellectual property—blockchain evidence is saved automatically when potential infringing contents are found[6]. According to Matej Michalko, in the previous trials of dispute cases, evidence preservation usually requires the involvement of a third-party authority such as a notary office, and relevant persons are required to fix the evidence under the witness of the notary. With the more frequent use of electronic evidence, most of the third-party electronic data preservation platforms have investigated the pattern of “block-chain + evidence 4 [www.jonasgross.medium.com/legal-aspects-of-blockchain-technology-part-1-blockchain-as-evidence-in-](http://www.jonasgross.medium.com/legal-aspects-of-blockchain-technology-part-1-blockchain-as-evidence-in-court-704ab7255cf5) [court-704ab7255cf5](http://www.jonasgross.medium.com/legal-aspects-of-blockchain-technology-part-1-blockchain-as-evidence-in-court-704ab7255cf5) 5 [https://blockchain24.pro/blokcheyn-i-yurisprudentsiya](https://blockchain24.pro/blokcheyn-i-yurisprudentsiya) 6 [https://www.lexology.com/library/detail.aspx?g=1631e87b-155a-40b4-a6aa-5260a2e4b9bb](https://www.lexology.com/library/detail.aspx?g=1631e87b-155a-40b4-a6aa-5260a2e4b9bb) ----- JANUS.NET, e journal of International Relations e-ISSN: 1647-7251 Vol. 14, Nº. 1 (May-October 2023), pp. 279-288 _Notes and Reflections_ _Problems of evaluation of digital evidence based on blockchain technologies_ Otabek Pirmatov collection and preservation”, which is applying blockchain technology to the traditional electronic evidence preservation practice (i.e., uploading the preserved evidence to a block-chain platform). If it is necessary, you can apply online for an expert opinion from the judicial expertise center. (Michalko, 2019: 7). Today, the task of providing electronic evidence before the court is carried out by notaries. Data recorded on a blockchain is in essence a chronological chain of digitally signed transactions. Thus, admissibility of block-chain evidence is highly correlated to acceptance of electronic signatures in a legal setting. Not all electronic signatures provide the same level of assurance. (Murray, 2016: 517-519). The usage of this technology when concluding transactions or receiving any official documents from the state greatly simplifies the process of proof, as it allows to track the entire history of changes made to the information stored in the blockchain. It also reliably protects them from illegal attempts to tamper or forge. Such evidence will be nearly impossible to challenge, although the risk of hacking or fraudulent activity remains. Second, if the court session is conducted using video conferencing, the blockchain can be easily used by the participants in the court session. Given the development of remote technologies caused by the coronavirus pandemic, this situation must be taken into account. Thus, thanks to the use of blockchain, it is possible to significantly reduce the time for consideration of cases in courts, increase the transparency of court proceedings and ensure the necessary confidentiality of information. If the contracts concluded by the parties are based on the blockchain technology or if the state authorities draw up their documents based on the blockchain technology, then it would be possible to evaluate the blockchain technology as evidence by the courts. Now in our country, government bodies are signing their documents with Q-code. According to Boris Glushenkov, the successful implementation of the blockchain will also change the courts: firstly, there will be no need to make decisions for concrete things. Second, evidence changes: electronic evidence is viewed with skepticism in courts. Maybe blockchain can change that[7]. In civil litigation, evidence was evaluated as evidence only if it met each of the criteria of relevance, admissibility, and reliability. Likewise, numerical evidence must meet the requirements of relevance, acceptability, and reliability of evidence evaluation criteria. Failure to evaluate digital evidence with one of the evidentiary evaluation criteria may result in its inadmissibility as evidence in court. According to Yuhei Okakita, In civil litigation, any form of evidence can generally be submitted to the court. That is, the court accepts not only physical documents but also digital data as evidence. Of course, civil procedure laws vary from country to country, but electronic evidence is recognized in many legislations such as the EU, the United States, or Japan. Since it can be said that blockchain certificates are a kind of digital data, it should be accepted in most courts as admissible evidence. 7 [https://blockchain24.pro/blokcheyn-i-yurisprudentsiya](https://blockchain24.pro/blokcheyn-i-yurisprudentsiya) ----- JANUS.NET, e journal of International Relations e-ISSN: 1647-7251 Vol. 14, Nº. 1 (May-October 2023), pp. 279-288 _Notes and Reflections_ _Problems of evaluation of digital evidence based on blockchain technologies_ Otabek Pirmatov So, you can submit the certificate to the court. However, the question is how judges evaluate the evidence. Let's to through an example relevant for e.g. the German or Japanese system: in these systems, it is up to the discretion of the judge to decide whether the certificate will be taken into consideration. If the judge believes the authenticity of the certificate, it will become the basis of the judgment. Let's suppose that the claim of a defendant in a dispute could be validated with the data certified with a blockchain transaction. The judge decides on the authenticity of the submitted evidence based on the opinions of both parties. The defendant will explain the concept of blockchain immutability achieved with the consensus mechanism, and the other party will argue the possibility that the information on the blockchain has been tampered with. After the judge considers both stories and takes a position regarding the authenticity of the information, s/he will make a decision accordingly[8]. According to Zihui (Katt) Gu, For the blockchain evidence to be admissible, the authenticity of the source of the electronic data must first be confirmed, whether through examination of the original or comprehensive consideration of all the evidence at hand[9]. The admissibility of digital evidence is one of the problems of judicial evaluation of evidence in civil litigation. In ensuring the admissibility of electronic evidence in foreign countries, transferring it to the blockchain software or evaluating the evidence in the blockchain software as admissible evidence is of great importance. According to Van Yojun, if blockchain technology can be applied to any digital evidence, regardless of whether it is a criminal or civil trial, the general expected benefits can be achieved, including: ensuring the integrity and accuracy of data, preventing the tampering of data or evidence, increasing the transparency of legal proceedings, Court proceedings are easy to follow, accelerated and simplified[10]. ## 2. Issues of application of blockchain technology in the legislation of foreign countries The Federal Government of the United States has not exercised its constitutional power to implement legislation regulating the admissibility of blockchain evidence in court. Thus, states enjoy residual power to implement their own legislation. The Federal Rules of Evidence establish a minimum requirement in what is referred to as the ‘best evidence rule which establishes that the best evidence must be used at trial. Rule 1002 of the Federal Rules of Evidence states “An original writing, recording, or photograph is required in order to prove its content unless these rules or a federal statute provides otherwise”. Several states have regulated blockchain through introducing their own legislation and rules, particularly with regard to the regulation of cryptocurrency – or as termed by various legislators, virtual currencies. New York kickstarted legislative developments in 8 [https://www.bernstein.io/blog/2020/1/17/can-digital-data-stored-on-blockchain-be-a-valid-evidence-in-](https://www.bernstein.io/blog/2020/1/17/can-digital-data-stored-on-blockchain-be-a-valid-evidence-in-ip-litigation) [ip-litigation](https://www.bernstein.io/blog/2020/1/17/can-digital-data-stored-on-blockchain-be-a-valid-evidence-in-ip-litigation) 9 [http://illinoisjltp.com/timelytech/blockchain-based-evidence-preservation-opportunities-and-concerns/](http://illinoisjltp.com/timelytech/blockchain-based-evidence-preservation-opportunities-and-concerns/) 10 [https://www.ithome.com.tw/news/130752](https://www.ithome.com.tw/news/130752) ----- JANUS.NET, e journal of International Relations e-ISSN: 1647-7251 Vol. 14, Nº. 1 (May-October 2023), pp. 279-288 _Notes and Reflections_ _Problems of evaluation of digital evidence based on blockchain technologies_ Otabek Pirmatov the USA through the regulation of virtual currency companie, and eventually several states followed suit, with 32 states implementing their own rules and regulations. The states of Illinois, Vermont, Virginia, Washington, Arizona, New York and Ohio have passed or introduced legislation which specifically regulates the admissibility of blockchain evidence in court[11]. In April 2018, 1 22 member states signed the Declaration for a European Blockchain Partnership (EBP) in order to “cooperate on the development of a European Blockchain Services Infrastructure.”2 With its ambitious goal of identifying initial use cases and developing functional specifications by the end of the year, the EBP should be an important catalyst for the use of blockchain technology by European government agencies[12]. In October 2018, discussions were underway among the Azerbaijani Internet Forum (AIF) for the Ministry of Justice to implement blockchain technology in several departments within its remit. Currently, the Ministry provides more than 30 electronic services and 15 information systems and registries, including “electronic notary, electronic courts, penitentiary service, information systems of non-governmental organizations”, and the register of the population, among others. Part of the AIF’s plans is to introduce a “mobile notary office” which would involve the notarization of electronic documents. Through this process, the registry’s entries will be stored on blockchain which parties will be able to access but not change, thus preventing falsification. Future plans also include employing smart contracts in public utility services such as water, gas and electricity[13]. Blockchain technology is a new way to build a network. Today, almost all service systems in the Internet system work on the basis of a centralized network, that is, the data warehouse is located on a central server, and users receive data by connecting to this server. The main difference of blockchain technology is that there is no need for a central server and all network participants have equal rights. The network database is kept by each user. One of the main reasons why evidence based on blockchain technology is considered admissible by courts is that blockchain technology is transparent, that is, it is not affected by the human factor. According to the Decision of the President of the Republic of Uzbekistan dated July 3, 2018, "On measures to develop the digital economy in the Republic of Uzbekistan": − basic concepts in the field of "blockchain" technologies and principles of its operation; − powers of state bodies, as well as process participants in the field of "blockchain" technologies; − measures of responsibility for using "blockchain" technologies for illegal purposes. The State Services Agency of the Republic of Uzbekistan has decided that starting from December 2020, the country's registry offices will operate based on blockchain technology. However, as of today, this system has not yet been launched. It would be 11 [https://blog.bcas.io/blockchain_court_evidence](https://blog.bcas.io/blockchain_court_evidence) 12 [https://www.eublockchainforum.eu/reports](https://www.eublockchainforum.eu/reports) 13 [https://blog.bcas.io/blockchain_court_evidence](https://blog.bcas.io/blockchain_court_evidence) ----- JANUS.NET, e journal of International Relations e-ISSN: 1647-7251 Vol. 14, Nº. 1 (May-October 2023), pp. 279-288 _Notes and Reflections_ _Problems of evaluation of digital evidence based on blockchain technologies_ Otabek Pirmatov appropriate if the documents issued not only by registry authorities, but also by tax authorities, cadastral departments, transactions concluded by notary offices, and most importantly, decisions of district and city mayors and reports issued by electronic auction, e-active, would be accepted based on blockchain technology. Agreements concluded by notary offices in civil courts, decisions of district and city mayors, and reports issued by electronic auction serve as the main written evidence confirming ownership rights. Due to the widespread involvement of information technologies in all spheres of social life in our country, the above bodies are also moving to receive documents in electronic form. Also, distribution of electricity based on blockchain technology is being carried out in Uzbekistan based on South Korean technology. Perhaps, in the future, electricity contracts in our country may be concluded on the basis of blockchain technology. ## 3. Discussion With the development of the Internet and information technology, digital data has gradually become an important part of the evidence system in civil court cases, which cannot be ignored. Among all types of digital data, blockchain evidence is a relatively new type. A proper blockchain is not a proof itself, but a technical implementation method of storing, transporting and correcting digital data. Blockchain is just a storage technology, the purpose of which is to ensure the authenticity and reliability of digital data. The most important thing is to determine the authenticity of the digital data. Improvements in blockchain technology can make electronic documents flow more quickly and improve the efficiency of their assessment in courts. However, compared to the traditional notarization method of securing electronic evidence, blockchain-based evidence storage lags behind. That is, there are not enough normative legal documents on the implementation of blockchain technologies in the field of justice. Notarization, which has become a means of preventing falsification of electronic documents, is rarely used in legal practice, because notarization of electronic evidence requires excessive time and money for the parties. It includes digital signatures, reliable time stamps and hash value verification to prove the authenticity of the submitted data using blockchain technology. Parties must be able to demonstrate how blockchain technology has been used to collect and store evidence. Due to the decentralization of information in the blockchain network, it is very difficult for hackers to exploit. Additionally, since each block contains the hash of the previous block, any transaction within the blockchain is done by changing it. Check Hash Value: After computing any electronic file using hash algorithm, only one hash value can be obtained. If the content of the electronic file changes, the resulting hash value will also change. The uniqueness and non-repeatability of the hash value ensures the immutability of electronic files. ----- JANUS.NET, e journal of International Relations e-ISSN: 1647-7251 Vol. 14, Nº. 1 (May-October 2023), pp. 279-288 _Notes and Reflections_ _Problems of evaluation of digital evidence based on blockchain technologies_ Otabek Pirmatov The verifier can use the hash value written to the blockchain to verify the original data to verify that the data is valid and has not been tampered with. Encrypting evidence can also ensure its safe storage. At a basic level, encryption uses a secret key to ensure that only those with access can read the file by encrypting the file's contents. It is possible to prepare documents based on blockchain technology in applications such as SharpShark, SynPat, WordProof, Waves, EUCD, DMCA. The main reason why evidence based on blockchain technology is considered acceptable evidence in foreign countries is its technological structure. We can see the following unique features of it: - at the discretion of one of the parties, it is not possible to change and add (falsify and destroy) documents based on blockchain technology; - documents based on blockchain technology are a technology resistant to hacker attacks, which means that electronic evidence based on blockchain technology cannot be tampered with by third parties; - in blockchain technology, there is no need for a central server, and all network participants have equal rights. A network database stores every user in it. The lack of possibility of falsification and alteration of the evidence based on blockchain technology makes it considered acceptable evidence by the courts. According to the civil procedural law, the admissibility of the evidence must be confirmed by certain means of proof according to this law. In order to ensure the admissibility of electronic evidence, it is appropriate to create electronic documents, electronic transactions using blockchain technology, and to improve the legislation in this regard. The following features of blockchain evidence should be considered: 1. To review the authenticity of the blockchain evidence. Specifically, it means that the court should examine whether the blockchain evidence is likely to be tampered with in the process of formation, transmission, extraction and display, and to the extent of such possibility. 2. To review the legitimacy of the blockchain evidence. Specifically, it means that the court should examine whether the collection, storage and extraction methods of blockchain evidence comply with the law, and whether they infringe on the legitimate rights and interests of others. 3. To review the relevance of blockchain evidence. Specifically, it means that the court should examine whether there is a substantial connection between the blockchain evidence and the facts to be proved[14]. 14 [https://www.chinajusticeobserver.com/a/when-blockchain-meets-electronic-evidence-in-china-s-internet-](https://www.chinajusticeobserver.com/a/when-blockchain-meets-electronic-evidence-in-china-s-internet-courts) [courts](https://www.chinajusticeobserver.com/a/when-blockchain-meets-electronic-evidence-in-china-s-internet-courts) ----- JANUS.NET, e journal of International Relations e-ISSN: 1647-7251 Vol. 14, Nº. 1 (May-October 2023), pp. 279-288 _Notes and Reflections_ _Problems of evaluation of digital evidence based on blockchain technologies_ Otabek Pirmatov ## Conclusion Blockchain storage solves the problem of securely storing digital data. In a sense, blockchain storage is an authentication or auxiliary storage method. Currently, blockchain storage is a more indirect authentication method. One of the peculiarities of blockchain technology in legal science is that the use of this technology when concluding transactions or obtaining any official documents from government authorities greatly simplifies the process of proof. Due to this, the blockchain allows to track the entire history of changes made to the data stored in the "data" and reliably protects against illegal attempts to tamper with or falsify the data. Such evidence would be nearly impossible to challenge, but the risk of hacking or fraudulent activity remains, albeit partially. Second, if court hearings are held online, the possibility of blockchain use by court hearing participants will increase even more. Thus, due to the use of blockchain, it is possible to significantly reduce the time of consideration of cases in civil courts and to increase the transparency of judicial processes and ensure the necessary confidentiality of information. Because public offering of goods and services on social networks has become popular in our country. Purchase of goods and services on social networks is carried out through mutual correspondence. Correspondence in the social network can be deleted or changed. This creates problems in evaluating social network correspondence as evidence in civil courts. The adoption of blockchain technologies by social networks may also lead to the use of social media correspondence as evidence in courts in the future. ## References Blockchain 24, consulted online, available at [https://blockchain24.pro/blokcheyn-i-](https://blockchain24.pro/blokcheyn-i-yurisprudentsiya) [yurisprudentsiya](https://blockchain24.pro/blokcheyn-i-yurisprudentsiya) Chan, Viviene (2020). Blockchain Evidence in Internet Courts in China: The Fast Track for Evidence Collection for Online Disputes. Consulted online, available at [https://www.lexology.com/library/detail.aspx?g=1631e87b-155a-40b4-a6aa-](https://www.lexology.com/library/detail.aspx?g=1631e87b-155a-40b4-a6aa-5260a2e4b9bb) [5260a2e4b9bb](https://www.lexology.com/library/detail.aspx?g=1631e87b-155a-40b4-a6aa-5260a2e4b9bb) De Filippi, Primavera and Wright, Aaron (2018). _Blockchain and the Law: The Rule of_ _Code. Harvard University Press._ Du, Guodong and Yu, Meng (2021). “When Blockchain Meets Electronic Evidence in China's Internet Courts”, China Justice Observer Consulted online, available at [https://www.chinajusticeobserver.com/a/when-blockchain-meets-electronic-evidence-](https://www.chinajusticeobserver.com/a/when-blockchain-meets-electronic-evidence-in-china-s-internet-courts) [in-china-s-internet-courts](https://www.chinajusticeobserver.com/a/when-blockchain-meets-electronic-evidence-in-china-s-internet-courts) European Union blockchain observatory & forum, blockchain for government and public [services (Dec. 7, 2018), https://www.eublockchainforum.eu/reports](https://www.eublockchainforum.eu/reports) ----- JANUS.NET, e journal of International Relations e-ISSN: 1647-7251 Vol. 14, Nº. 1 (May-October 2023), pp. 279-288 _Notes and Reflections_ _Problems of evaluation of digital evidence based on blockchain technologies_ Otabek Pirmatov Fedorov, Pavel (2022). “What is blockchain: everything you need to know about the technology”, Forbes, consulted online, available at [https://www.forbes.ru/mneniya/456381-cto-takoe-blokcejn-vse-cto-nuzno-znat-o-](https://www.forbes.ru/mneniya/456381-cto-takoe-blokcejn-vse-cto-nuzno-znat-o-tehnologii) [tehnologii](https://www.forbes.ru/mneniya/456381-cto-takoe-blokcejn-vse-cto-nuzno-znat-o-tehnologii) Gazeta.uz (2022). Blockchain technology is not a problem, but it is a problem that has _to_ _be_ _solved._ Consulted online, available at [https://www.gazeta.uz/uz/2022/08/26/blockchain-technology/](https://www.gazeta.uz/uz/2022/08/26/blockchain-technology/) # Gross, Jonas (2020). Legal aspects of blockchain technology. Consulted online, availabe at [www.jonasgross.medium.com/legal-aspects-of-blockchain-technology-part-1-](http://www.jonasgross.medium.com/legal-aspects-of-blockchain-technology-part-1-blockchain-as-evidence-in-court-704ab7255cf5) [blockchain-as-evidence-in-court-704ab7255cf5](http://www.jonasgross.medium.com/legal-aspects-of-blockchain-technology-part-1-blockchain-as-evidence-in-court-704ab7255cf5) Gulyamov, S. (2019). Blockchain technologies in the digital economy. Textbook, p. 114. iThome (2022). Taiwan Takes the Lead in Judicial Blockchain Applications] An Inventory _of_ _Global_ _Judicial_ _Blockchain_ _Applications,_ consulted online, available at [https://www.ithome.com.tw/news/130752](https://www.ithome.com.tw/news/130752) Michalko, Matej (2019). “Blockchain ‘witness’: a new evidence model in consumer disputes”. International journal on consumer law and practice. V.7., p.7. Murray, Andrew (2016). Information Technology Law, p. 517-519. Okakita, Yuhei (2020). _Can digital data stored on Blockchain be valid evidence in IP_ _litigation?. Consulted online, available at_ [https://www.bernstein.io/blog/2020/1/17/can-](https://www.bernstein.io/blog/2020/1/17/can-digital-data-stored-on-blockchain-be-a-valid-evidence-in-ip-litigation) [digital-data-stored-on-blockchain-be-a-valid-evidence-in-ip-litigation](https://www.bernstein.io/blog/2020/1/17/can-digital-data-stored-on-blockchain-be-a-valid-evidence-in-ip-litigation) Pollacco, Alexia (2020). _The Interaction between Blockchain Evidence and Courts – A_ _cross-jurisdictional_ _analysis._ _Consulted_ _online,_ _available_ _at_ [https://blog.bcas.io/blockchain_court_evidence](https://blog.bcas.io/blockchain_court_evidence) _The Illinois Journal of Law, Technology & Policy, consulted online, available at_ [http://illinoisjltp.com/timelytech/blockchain-based-evidence-preservation-](http://illinoisjltp.com/timelytech/blockchain-based-evidence-preservation-opportunities-and-concerns/) [opportunities-and-concerns/](http://illinoisjltp.com/timelytech/blockchain-based-evidence-preservation-opportunities-and-concerns/) How to cite this note Pirmatov, Otabek (2023). Problems of evaluation of digital evidence based on blockchain technologies. Notes and Reflections in Janus.net, e-journal of international relations. Vol. 14, Nº 1, May-October 2023. Consulted [online] on date of last visit, [https://doi.org/10.26619/1647-](https://doi.org/10.26619/1647-7251.14.1.01) [7251.14.1.01](https://doi.org/10.26619/1647-7251.14.1.01) -----	Problems of evaluation of digital evidence based on blockchain technologies		2023.0	NaT	https://www.semanticscholar.org/paper/0002c60ed10a8868930b8f971af29e62b498f6b8	JANUS NET e-journal of International Relation	True
000523657fe1a5879d72c099f619ea0de4424bff	ERROR: type should be string, got "https://doi.org/10.1007/s13762 022 04079 x\n\nREVIEW\n\n# Plastic waste recycling: existing Indian scenario and future opportunities\n\nR. Shanker[2] · D. Khan[2] · R. Hossain[1] · Md. T. Islam[1] · K. Locock[3] · A. Ghose[1] · V. Sahajwalla[1] · H. Schandl[3] ·\nR. Dhodapkar[2]\n\nReceived: 13 December 2021 / Revised: 23 February 2022 / Accepted: 4 March 2022 / Published online: 2 April 2022\n© The Author(s) under exclusive licence to Iranian Society of Environmentalists (IRSEN) and Science and Research Branch, Islamic Azad University 2022\n\nAbstract\nThis review article aims to suggest recycling technological options in India and illustrates plastic recycling clusters and reprocessing infrastructure for plastic waste (PW) recycling in India. The study shows that a majority of states in India are engaged\nin recycling, road construction, and co-processing in cement kilns while reprocessing capabilities among the reprocessors\nare highest for polypropylene (PP) and polyethylene (PE) polymer materials. This review suggests that there are key opportunities for mechanical recycling, chemical recycling, waste-to-energy approaches, and bio-based polymers as an alternative\nto deliver impact to India’s PW problem. On the other hand, overall, polyurethane, nylon, and polyethylene terephthalate\nappear most competitive for chemical recycling. Compared to conventional fossil fuel energy sources, polyethylene (PE),\npolypropylene (PP), and polystyrene are the three main polymers with higher calorific values suitable for energy production.\nAlso, multi-sensor-based artificial intelligence and blockchain technology and digitization for PW recycling can prove to be\nthe future for India in the waste flow chain and its management. Overall, for a circular plastic economy in India, there is a\nnecessity for a technology-enabled accountable quality-assured collaborative supply chain of virgin and recycled material.\n\nKeywords Informal and formal sector · Biological recycling · Chemical recycling · Mechanical recycling · Digitization ·\nBlockchain technology\n\n\n### Introduction\n\nPlastic has evolved into a symbol of human inventiveness as\nwell as folly which is an invention of extraordinary material\nwith a variety of characteristics and capacities. Although\nIndia is a highly populated country, it is ranked 12th among\nthe countries with mismanaged plastics but it is expected\n\nEditorial responsibility: Maryam Shabani.\n\n- D. Khan\nk.debishree@neeri.res.in\n\n1 Centre for Sustainable Materials Research and Technology,\nSMaRT@UNSW, School of Materials Science\nand Engineering, UNSW Sydney, Sydney, NSW 2052,\nAustralia\n\n2 Council of Scientific and Industrial Research-National\nEnvironmental Engineering Research Institute\n(CSIR-NEERI), Nehru Marg, Nagpur 440 020, India\n\n3 Commonwealth Scientific and Industrial Research\nOrganisation (CSIRO) and Australian National University,\nCanberra, ACT 2601, Australia\n\n\nthat by the year 2025, it will be in 5th position (Neo et al.\n2021). Therefore, recycling or upscaling, or reprocessing of\nPW has become the urgency to curb this mismanagement\nof plastics and mitigate the negative impacts of plastic consumption and utilization from the environment. However,\nthis resource has not been given the required attention it\ndeserves after post-consumer use. Recycling or reprocessing\nof PW usually involves 5 types of processes based on the\nquality of the product manufactured upon recycling of the\nwaste, namely upgrading, recycling (open or closed loop),\ndowngrading, waste-to-energy plants, and dumpsites or\nlandfilling, as shown in Fig. 1 (Chidepatil et al. 2020). Usually, the PW is converted into lower-quality products such\nas pellets or granules, or flakes which are further utilized in\nthe production of various finished products such as boards,\npots, mats, and furniture (Centre for Science and Environment (CSE) 2021).\nPlastics have a high calorific value, with polymer energy\nvarying from 62 to 108 MJ/kg (including feedstock energy)\nwhich is much greater than paper, wood, glass, or metals\n(with exception of aluminum) (Rafey and Siddiqui 2021).\n\nV l (0123456789)1 3\n\n\n-----\n\nFig. 1 Different processing\npathways for plastic waste\n(modified from Chidepatil et al.\n2020)\n\nPW mishandling is a significant concern in developing\nnations like India due to its ineffective waste management\ncollection, segregation, treatment, and disposal which\naccounts for 71% of mishandled plastics in Asia (Neo et al.\n2021). Though there are numerous sources for PW the major\nfraction is derived from the post-consumer market which\ncomprises both plastic and non-PWs and therefore, these\nwastes require to be washed and segregated accordingly\nfor conversion into the homogenous mixture for recycling\n(Rafey and Siddiqui 2021). According to a study carried out\nby the Federation of Indian Chambers of Commerce and\nIndustry (FICCI) and Accenture (2020), India is assumed to\nlose over $133 billion of plastic material value over the coming next 10 years until 2030 owing to unsustainable packaging out of which almost 75% of the value, or $100 billion,\ncan be retrieved. This review article focuses on levers and\nstrategies that could be put in place to transition India toward\na circular economy for plastics. This involves two key areas,\nthe first being reprocessing infrastructure in various states\nof India and the performance of the reprocessors in organized and unorganized sectors. The second key area for this\nstudy is an overview of the rapidly evolving area of plastic\nrecycling technologies, including mechanical recycling,\nchemical recycling, depolymerization, biological recycling,\nand waste-to-energy approaches. A brief description of the\ntechnologies is provided and their applicability to the Indian\ncontext discussed along with the role of digitization in PW\nrecycling.\n\n## 1 3\n\n\n### Research motivation and scope of the article\n\nThe research on Indian PW and its recycling pathways\naccording to the polymer types and its associated fates were\nstudied along with the published retrospective and prospective studies. Due to COVID-19, there is an exponential\nincrease in the PW and the urge to recycle this waste has\nbecome a necessity. Systematic literature studies from database collection of Web of Science (WoS) were performed\nwith keywords such as “PW recycling technologies in India”\nOR “PW management in India” OR “plastic flow in India”\nfrom 2000 to October 2021 (including all the related documents such as review papers, research papers, and reports)\nwhich in total accounted for 2627 articles only. When the\nsame keyword “plastic recycling” was searched without\ncontext to India, 5428 articles were published from 2000\nto 2021 among which only 345 articles were published by\nIndian authors. Figure 2 shows the distribution of papers on\nPW and related articles over the years. However, the number\nof review articles remains very limited concerning published\nresearch papers and reports for the same. Review articles\nplay a vital role in the substantial growth in the potential\nresearch areas for the enhancement of the proper management strategies in the respective domains. Recently, PW\nand its sustainable management necessity toward achieving\na circular economy have attracted researchers, due to its detrimental effects on humans and the environment.\n\n\n-----\n\nFig. 2 Yearly distribution of\npapers related to plastic waste\nrecycling from 2000 to October\n2021\n\n\n640\n\n600\n\n560\n\n520\n\n480\n\n440\n\n400\n\n360\n\n320\n\n280\n\n240\n\n200\n\n160\n\n120\n\n\n### Reprocessing infrastructure and recycling rates for different types of plastics\n\nRecycling rates of plastics vary between countries depending upon the types of plastic. Some polymers are recycled\nmore than other types of polymers due to their respective\ncharacteristics and limitations. While PET (category 1) and\nHDPE (high-density polyethylene) (category 2) are universally regarded as recyclable, PVC (polyvinyl chloride) (category 3) and PP (category 5) are classified as “frequently\nnot recyclable” owing to their chemical characteristics, however, they may be reprocessed locally depending on practical\nconditions. LDPE (low-density polyethylene) (category 4)\nis however difficult to recycle owing to stress failure, PS\n(category 6) may or may not be recyclable locally, and other\ntypes of polymers (category 7) are not recyclable due to the\nvariety of materials used in its manufacturing (CSE 2021).\nAbout 5.5 million metric tonnes of PW gets reprocessed/\nrecycled yearly in India, which is 60% of the total PW produced in the country where 70% of this waste is reprocessed\nin registered (formal) facilities, 20% by the informal sector\nand the rest 10% is recycled at household level (CSE 2020).\nThe remaining 40% of PW ends up being uncollected/littered, which further results in pollution (water and land) and\nchoking of drains (CSE 2019a). PW is dumped into landfills\nat a rate of 2.5 million tonnes per year, incinerated at a rate\nof over 1 million tonnes per year, and co-processed as an\nalternative energy source in blast furnaces at a rate of 0.25\nmillion tonnes per year by cement firms (Rafey and Siddiqui\n2021). Thermoset plastics (HDPE, PET, PVC, etc.), which\n\n\n110 119\n85 [102 ]86 87\n76\n66\n\n35 41\n1 5 8 5 4 7 4 11 14 11 15 22\n\nResearch Paper Review Articles\n\nare recyclable, constitute 94% of total PW generated, and\nthe remaining 6% comprises other types of plastics which\nare multilayered, thermocol, etc. and are non-recyclable\n(CSE 2019b). Plastics such as PP, PS, and LDPE are partially recyclable but generally not recycled in India due to\nthe economic unviability of their recycling processes (CSE\n2020). Figure 3a shows the recycling rates of different kinds\nof plastics in India and Fig. 3b shows the percentage contribution of different recycling options in the Indian context.\n\n#### State‑wise facilities and flows of PW\n\nThe total plastic generation in India by 35 states and union\nterritories accounts for 34,69,780 tonnes/annum (~ 3.47 million tonnes/annum) in the year 2019–2020 (CPCB (Central\nPollution Control Board) 2021). Plastic processing in India\nwas 8.3 Mt in the 2010 financial year and increased to 22 Mt\nin 2020 (Padgelwar et al. 2021). Table 1 shows the state-wise\nPW generation, registered and unregistered plastic manufacturing/recycling units, and multiplayer manufacturing units\nacross the country. Furthermore, the main recycling clusters\nin India are presented in Fig. 4, wherein Gujarat (Dhoraji,\nDaman and Vapi), Madhya Pradesh (Indore), Delhi and\nMaharashtra (Malegaon, Mumbai (Dharavi and Bhandup),\nSolapur) are the main recycling hubs (Plastindia Foundation\n2018). Recycling processes and disposal methods for PW\nvary substantially across the states in India given in Table 1.\nDetails of some of the major infrastructure available in the\nstates are described in the following subsection.\n\n## 1 3\n\n\n-----\n\nFig. 3 a Recycling rates of\ndifferent types of plastics in (a) 2.4%\nIndia (data extracted from CSE 7.6%\n2019b) and b percentage contribution of different recycling\noptions in the Indian context\n(CSE 2021)\n\n25%\n\n20%\n\nPVC HDPE\n\nThe door-to-door collection of solid waste is the most\ncommon practice for the collection of waste in almost all the\nstates. Urban Local Bodies (ULBs) of some states like Goa,\nHimachal Pradesh, Maharashtra, Uttarakhand, and West\nBengal are actively involved in the collection and segregation of waste (CPCB 2019; Goa SPCB 2020; MPCB 2020).\nFurther after collection and segregation of waste, the PW is\nsent to various disposal (landfills) and recycling pathways\n(recycling through material recovery, road construction,\nwaste-to-energy plants, RDF (refused derived fuel), etc.).\nGoa is the state where new bailing stations have been set up\nin addition to the existing facilities for the disposal of PW\n(Goa SPCB 2020). State like Kerala has taken the initiative\nfor the installation of reverse vending machines (RVMs) for\nplastic bottles in supermarkets and malls whereas Maharashtra ensures 100% collection of waste with proper segregation and transport of PW where 62% of the waste is being\nreprocessed through different methods (Kerala SPCB 2020;\nMPCB 2020). Special Purpose Vehicles (SPVs) in Punjab\nhave been effective for the collection of multilayered plastics\n(MLP) waste from different cities of the state and further\nbeing sent to waste-to-energy plants (Punjab Pollution Control Board (PPCB) 2018). Though almost all the states have\nimposed a complete ban on plastic bottles and bags, Sikkim\nwas the first state who enforce the ban into the state which\nresulted in the reduction in its carbon footprint (MoHUA\n2019). Many states such as Puducherry, Odisha, Tamil Nadu,\nTelangana, Uttar Pradesh, and West Bengal send their PW\nfor reprocessing in cement kilns (CPCB 2019). Some states\nlike Telangana have taken the initiative for source segregation of the waste from the households by separating the\nbins into dry and wet waste bins whereas the mixed waste\nis sent for further processing for road construction or in\ncement industries (Telangana State Pollution Control Board\n\n## 1 3\n\n\n(TSPCB) 2018). Along with all these facilities in different\nstates, several informal and unregistered recyclers are also\ncontributing to their best to combat PW mismanagement.\n\n#### Formal and informal sectors in India and their performance\n\nThe informal sector currently contributes 70% of PET recycling in India (Aryan et al. 2019). Approximately 6.5 tonnes\nto 8.5 tonnes per day of PW is collected by itinerant waste\nbuyers (IWBs) and household waste collectors in India, out\nof which 50–80% of PW is recycled (Nandy et al. 2015).\nKumar et al. (2018) mentioned that the average PW collected\nby a waste picker and an IWB was approximately 19 kg/d\nand 53 kg/d, respectively. According to ENF (2021), there\nare approximately 230 formal PW reprocessors in India,\nwho can recycle various types of the polymer as shown in\nFig. 5. However, the organized and unorganized sectors play\na vital role in the reprocessing of plastics in India. Table 2\nshows the distribution of organized and unorganized sectors along with the percentage growth in India. Most of the\noperations are currently related to mechanical recycling producing granules/pellets and flakes. In 30 states/UTs, there\nare 4953 registered units with 3715 plastic manufacturers/\nproducers, 896 recyclers, 47 compostable manufacturing,\nand 295 multilayered packaging units however, 823 unregistered units have been reported from different states (CPCB\n2021). However, data on reprocessing capability (material\nprocessed in terms of tonnes/year) of the individual recyclers\nare not readily available. With the limited data, it varies from\n2500 to 3000 tonnes/year whereas capacity for processing\nvarious PW varies from 600 to 26,250 tonnes/year (ENF\n2021).\n\n\n-----\n\nTable 1 Plastic generation, plastic manufacturing, and recycling units in different states in India and status of plastic recycling and disposal in\ndifferent states\n\n\nPossible recycling and\ndisposal methods involved\n\n\nMultilayer\nmanufacturing\nunits\n\n\nStates/UT Plastic generation (tonnes/\nannum)\n\n\nRegistered plastic manu- Unregistered plastic\nfacturing/recycling units manufacturing/recycling\nunits\n\n\nAndaman and Nicobar 386.85 – – – Recycling, Road construction\nAndhra Pradesh 46,222 Manufacturing units— – – Recycling, Road construc131 tion, Co-processing in\nCompostable units—1 cement kilns\n\nArunachal Pradesh 2721.17 – – – No information\nAssam 24,970.88 Manufacturing units—18 – 5 Road construction, Coprocessing in cement\nkilns\nBihar 4134.631 Manufacturing/Recycling Producers—225 – No information\nunits—8 Brand owners—203\nRecyclers—36\n\nChandigarh 6746.36 Recycling units—7 – – RDF processing plant\nChhattisgarh 32,850 Manufacturing units—8 – – Recycling, Co-processing\nRecycling units—8 in cement kilns, Wasteto-energy plant\nDaman Diu & Dadra 1947.7 343 – – No information\nNagar Haveli\n\nDelhi 230,525 Producers—840 – – Waste-to-energy plant\nGoa 26,068.3 Manufacturing units—35 – 1 Recycling, Co-processing\nCompostable unit—1 in cement kilns, Sanitary landfills\nGujarat 408,201.08 Manufacturing/Recycling – 10 Co-processing in cement\nunits—1027 kilns\nCompostable units—12\n\nHaryana 147,733.51 Manufacturing units—69 – 28 Road construction\nCompostable unit—1\n\nHimachal Pradesh 13,683 No information 24 79 Road construction, Coprocessing in cement\nkilns, Waste-to-energy\nplants\nJammu & Kashmir 74,826.33 259 45 – No information\nJharkhand 51,454.53 Manufacturing units—59 – – Road construction, Coprocessing in cement\nkilns, Reverse Vending\nMachines\nKarnataka 296,380 Manufacturing/Recycling 91 – Recycling, Co-processing\nunits—163 plants\nKerala 131,400 Manufacturing units— – – Recycling\n1266\nProducers—82\nRecycling units—99\nCompostable unit—1\n\nLakshadweep 46 – – – Recycling\nMadhya Pradesh 121,079 Manufacturing and Recy- – 22 Recycling, Road construccling units—164 tion, Co-processing in\nCompostable unit—1 cement kilns\n\nMaharashtra 443,724 Recycling units—62 42 – No information\nCompostable manufacturing units—6\n\nManipur 8292.8 Manufacturing units—4 – – No information\nMeghalaya 1263 4 – – Road construction\nMizoram 7908.6 – – – Recycling\n\n## 1 3\n\n\n-----\n\nTable 1 (continued)\n\nStates/UT Plastic generation (tonnes/\nannum)\n\n\nPossible recycling and\ndisposal methods involved\n\n\nRegistered plastic manu- Unregistered plastic\nfacturing/recycling units manufacturing/recycling\nunits\n\n\nMultilayer\nmanufacturing\nunits\n\n\nNagaland 565 Manufacturing units—4 – – Recycling, Road construction\nOdisha 45,339 Manufacturing units—13 – 3 Co-processing in cement\nkilns\nPunjab 92,890.17 Manufacturing/Recycling 48 4 Recycling\nunits—187\nCompostable units—2\nMaterial Recovery Facility—169\n\nPuducherry 11,753 Manufacturing/Recycling – 4 Road construction, Counits—49 processing in cement\nCompostable unit—1 kilns\n\nRajasthan 51,965.5 Manufacturing units—69 – 16 No information\nSikkim 69.02 – – – No information\nTamil Nadu 431,472 Manufacturing units—78 – 3 Recycling, Road construcRecycling units—227 tion, Co-processing in\ncement kilns\nTelangana 233,654.7 Manufacturing/Recycling – 2 Recycling, Road construcunits—316 tion, Co-processing in\ncement kilns\nTripura 32.1 Manufacturing units—26 – 2 No information\nRecycling units—4\n\n\nUttarakhand 25,203.03 Manufacturing/Recycling\nunits—33\nCompostable units—2\n\n\n15 28 Recycling\n\n\nUttar Pradesh 161,147.5 Manufacturing units—99 23 63 Road construction, CoRecycling units—16 processing in cement\nCompostable units—4 kilns, Waste-to-energy\n\nplant, Production of fibers and raw materials\nWest Bengal 300,236.12 Manufacturing/Recycling – 9 Road construction\nunits—157\nCompostable unit—1\n\nData sources: (Central Pollution Control Board 2019; Central Pollution Control Board 2021; CSE 2020; Goa State Pollution Control Board\n2020; Tamil Nadu Pollution Control Board 2020; Haryana State Pollution Control Board 2020; Jammu and Kashmir State Pollution Control\nBoard 2018; Kerala State Pollution Control Board 2020; Maharashtra Pollution Control Board 2020; Uttarakhand Pollution Control Board 2019;\nUttar Pradesh Pollution Control Board 2021)\n\n\nIn the Indian context, the scale of operation and quantity of material handled by the formal sector is insignificant\nwhen compared to the informal sector (Nallathambi et al.\n2018). However, data on the contribution of the informal\nsector in PW recycling in India are very limited (Kumar\net al. 2018). Formal recycling is constrained to clean, separated, pre-consumer waste in a few places in India, even if\nthe states have efficient recycling technology and resources,\nas in Gujarat and Maharashtra (TERI 2021). At present, the\ntotal numbers of organized and unorganized recycling units\nin India are 3500 and 4000, respectively (Satapathy 2017).\nThe formal recyclers face challenges in providing supply\nsecurity for reprocessed plastic materials as the current\nsupply is dominated by informal recyclers (TERI 2021). In\n\n## 1 3\n\n\nrecovering consumer waste (including PW), the informal\nsector and households play a vital role in the waste collection; approximately 6.5–8.5 Mt of PW are collected by\nthese entities, which is about 50–80% of the plastic produced\n(Nandy et al. 2015). PW collection, dismantling, sorting,\nshredding and cleaning, compounding, extrusions (pellet\nmaking) and new product manufacturing are the key activities done by the informal sector PW supply chain in India\n(WBCSD 2017).\nAmong the formal recyclers, Banyan Nation has implemented a proprietary washing technology to remove ink\nand markings from PW in the mechanical recycling process\n(Banyan Nation 2020). The recycler has integrated plastic recycling technology with data intelligence (real-time\n\n\n-----\n\nFig. 4 Plastic recycling clusters in India (Plastindia Foundation 2018)\n\nFig. 5 Number of reprocessors 120\naccording to polymer types\n\n104\n\nin India (ENF 2021). (Abbreviations: ABS: Acrylonitrile 100\nbutadiene styrene; HIPS: High 86\nimpact polystyrene; LLDPE: 80\nLinear low-density polyethyl- 73\nene; PA: Polyamide; PBT: Poly- 64\nbutylene terephthalate; SAN: 60\nStyrene acrylonitrile; POM:\nPolyoxymethylene; PMMA:\nPoly(methyl methacrylate); 40\nTPE: Thermoplastic elastomer)\n\n\n## 1 3\n\n\n-----\n\nTable 2 Distribution of organized and unorganized plastic recycling units in India (Plastindia Foundation 2019)\n\nParameters 2018 report 2019 report Percentage growth\n\nNo. of organized recycling units 3500 100 − 93%\nNo. of unorganized recycling units 4000 10,000 60%\nDirect manpower 600,000 100,000 − 83%\nIndirect manpower (including ragpickers) 1 million 1–1.5 million 50% (concerning upper limit)\nAmount of plastic waste recycled 5.5 million metric 6 million metric tonnes 8.3%\ntonnes\n\n\nlocation of informal sector PW collectors and their capacity\nfor waste processing), which has enhanced its performance\nin high-quality waste collection and recycling (Banyan\nNation 2020). The informal sector is largely involved in\nrecycling PET bottles (mainly collection and segregation).\nHorizontal turbo washers and aglow machines are widely\nused in PE granule production by the informal sector (Aryan\net al. 2019). The Alliance of Indian Waste Pickers comprises 30 organizations in 24 cities of the country, working\nin collaboration with waste pickers, acknowledging their\ncontribution, and urging for them to be integrated into the\nwaste management system. For the informal sector, a proper\ncollection network, linking GPS (Global Positioning System) to points of segregation, and tracking vehicles should\nbe considered in a consolidated framework (Jyothsna and\nChakradhar 2020).\nThe organized/formal and unorganized/informal sectors\nare not discrete and do not vie for waste; instead, they are\ninterdependent and coherent as the formal recyclers can\noperate because the informal sector performs the onerous\ntask of conveying utilizable PW to the formal sector in the\nform of aggregates, pellets, flakes and, in a few instances,\neven the finished product. Since formal commodities are\nthe ones who purchase their final goods, the informal sector relies on the formal sector. Furthermore, the informal\nsector's financial capability and ability to invest in infrastructure and equipment to manufacture goods on their own\nare restricted and therefore both communities have a mutual\nrelationship (CSE 2021).\n\n### Overview on plastic recycling technologies and their applicability to India\n\nFrom waste to material recovery, PW recycling can broadly\nbe categorized into mechanical recycling, chemical recycling, biological recycling, and energy recovery (Al-Salem\net al. 2017). The most preferable type of recycling is primary\nrecycling because of its contamination-free feature which\nfurther facilitates a smaller number of operating units resulting in the optimal amount of consumption of energy supply and resources which is further followed by secondary\n\n## 1 3\n\n\nrecycling (mechanical recycling) for recycling PW (CSE\n2021). However, processing difficulties and the quality\nof recyclates are the main drivers for seeking alternative\napproaches (Ragaert et al. 2017). Comparatively, tertiary\nrecycling or chemical/feedstock recycling is a less favored\nalternative because of high production and operational\ncosts, as well as the lack of scalable commercial technology in India whereas quaternary recycling which involves\nenergy recovery, energy from waste, or valorization of PW,\nis least preferred due to uncertainty around propriety and\nprominence of the technology, and the negative potential\nto convert land-based pollution to water and air pollution,\nbut anyhow more preferable than dumping into the landfill\n(Satapathy 2017; CSE 2021). Figure 6 shows the categorization of the recycling process of PW.\n\n#### Recycling technologies\n\nMechanical recycling (MR)\n\nMechanical recycling (also known as secondary, material\nrecycling, material recovery, or back-to-plastics recycling)\ninvolves physical processes (or treatments) that convert PW\ninto secondary plastic materials. It is a multistep process\ntypically involving collection, sorting, heat treatment with\nreforming, re-compounding with additives, and extruding\noperations to produce recycled material that can substitute\nfor virgin polymer (Ragaert et al. 2017; Faraca and Astrup\n2019). It is conventionally capable of handling only singlepolymer plastics, such as PVC, PET, PP, and PS. It remains\none of the dominant recycling techniques utilized for postconsumer plastic packaging waste (PlasticsEurope 2021).\nThere are various key approaches to sorting and separating\nPW for MR, including zig-zag separator (also known as an\nair classifier), air tabling, ballistic separator, dry and wet\ngravity separation (or sink-float tank), froth flotation, and\nelectrostatic separation (or triboelectric separation). There\nare also some newer sensor-based separation technologies\navailable for PW which include plastic color sorting and\nnear-infrared (NIR) (Ministry of Housing & Urban Affairs\n(MoHUA) 2019). Fig. S1 of the supplementary material\n\n\n-----\n\nFig. 6 Plastic waste flow and recycling categorization (Modified from FICCI 2016; Sikdar et al. 2020; Tong et al. 2020)\n\n\nshows the overall mechanical reprocessing infrastructure\nfor plastics.\nAfter the collected plastics are sorted, they are melted\ndown directly and molded into new shapes or are re-granulated (with the granules then directly reused in the manufacturing of plastic products). In the re-granulation process,\nplastic is melted down after being shredded into flakes, then\nprocessed into granules (Dey et al. 2020).\nDegradation and heterogeneity of PW create significant\nchallenges for recyclers involved in mechanical recycling\nas in many cases, recycled plastics do not have the same\nmechanical properties as virgin materials and therefore,\nseveral challenges emerge while recycling mono and mixed\nPW. Furthermore, difficulties in developing novel technologies to remove volatile organic compounds to improve the\nquality of recycled plastics is one of the key technological\nchallenges in mechanical recycling (Cabanes et al. 2020).\nDifferent polymers degenerate under their specific characteristics such as oxidation, light and heat, ionic radiation,\nand hydrolysis where thermal–mechanical degradation and\ndegradation during lifetime are the two ways by which it\n\n\noccurs while recycling or reprocessing of PW (Ragaert et al.\n2017). Faraca and Astrup (2019) also state that models to\npredict plastic performance based on the physical, chemical, and technical characteristics of PW will be critical in\noptimizing these processes. Other than technical challenges,\nthe mechanical recycling process possesses social and economic challenges such as sorting of mixed plastics, lack of\ninvestments and legislation, and quality of recycled products\n(Payne et al. 2019).\n\nChemical recycling\n\nChemical recycling, tertiary recycling, or feedstock recycling refers to the transformation of polymers into simple\nchemical structures (smaller constituent molecules) which\ncan be utilized in a diverse range of industrial applications\nand/or the production of petrochemicals and plastics (Bhagat\net al. 2016; Jyothsna and Chakradhar 2020). This type of\nrecycling directly involves fuel and chemical manufacturers\n(Bhagat et al. 2016). Pyrolysis, hydrogenation, and gasification are some of the chemical recycling processes (Singh\n\n## 1 3\n\n\n-----\n\nand Devi 2019). The food packaging sector could be the\nmain industry to utilize outputs from the chemical recycling\nprocess (BASF 2021).\nWhen molecules, combustible gases, and/or energy are\ngenerated in a thermal degradation process, molecules, combustible gases, and/or energy are generated as multi-stream\noutputs whereas layered and complex plastics, low-quality\nmixed plastics, and polluted plastics are all viable targets\nfor chemical/feedstock recycling (CSE 2021). From an\noperational standpoint, utilizing residual chars and no flue\ngas clean-up requirements are the main advantages, while\nfrom an environmental point of view, reduction in landfilling coupled with reduced GHGs (green-house gases) and\nCO2 (carbon dioxide) emissions are added benefits. Ease of\nuse in electricity and heat production and easily marketed\nproducts are some of the financial advantages of pyrolysis\n(Al-Salem et al. 2010). Plasma pyrolysis is a state-of-the-art\ntechnology in which thermo-chemical properties are being\nintegrated with pyrolysis (MoHUA 2019). Fig. S2 of the\nsupplementary material shows the chemical valorization of\nwaste plastics. Although, cost and catalyst reuse capability in pyrolysis processes need further investigation (TERI\n2020). Due to high energy requirements and the low price of\npetrochemical feedstock compared to monomers developed\nfrom waste plastics, chemical recycling is not yet common\nat an industry scale (Schandl et al. 2020).\nProcessing of mixed waste remains a difficult task due to\nthe intricacy in the reactions where different types of polymers reflect completely distinct spectra following degradation pathways (Ragaert et al. 2017). The presence of PVC in\nthe waste stream possesses another problem due to its density and removal of hydrochloric acid (HCl) from products\nand thus resulting in incomplete segregation (Ragaert et al.\n2017). Other than this, lack of stable waste supply, suitable\nreactor technology, and presence of inorganics in the waste\nstream possess challenges in the chemical recycling of the\nplastics (Payne et al. 2019). Lack of investments, production\nof by-products and metal-based catalysts systems contribute\nto other significant difficulties in the chemical valorization\nof waste plastics (Cabanes et al. 2020; Kubowicz and Booth\n2017).\n\nDepolymerization Depolymerization of the plastics is\nthe result of chemical processing where various monomer\nunits are recovered which can be reused for the production\nof new plastics manufacturing or conversion into their raw\nmonomeric forms through processes such as hydrolysis,\nglycolysis, and alcoholysis (Bhandari et al. 2021; Mohanty\net al. 2021). This process is often used to recover monomers from a recoverable resin's grade to that of virgin resin\nsuch as PET, polyamides such as nylons, and polyurethanes\nwith excellent results, as well as the possibility to restore a\nsignificant resource from commodities that are difficult to\n\n## 1 3\n\n\nrecycle commercially (MoHUA 2019). This is the process\nby which the plastic polymers are converted into sulfur-free\nliquid power sources through chemical recycling where\nthese power sources facilitate energy recovery from PWs\n(Bhandari et al. 2021). According to the studies carried out\non depolymerization of mixed waste plastics, it has been\nreported that even a small quantity, for instance, 1 mg of\nthese plastics can yield 4.5 to 5.9 cal of energy with a little\namount of energy consumption of 0.8–1 kWh/h and therefore, this process can yield additional convenience for the\nhigh-quality recycling which is recently being used for the\nPET (Bhandari et al. 2021; Ellen MacArthur Foundation\n2017; Wołosiewicz-Głąb et al. 2017). In the anoxic conditions and the presence of specific catalytic additives, the\ndepolymerization is accomplished in a specially modified\nreactor where 350 °C is the highest reaction temperature\nwhich is converted to either liquid RDF or different gases\n(reutilized as fuel) and solids (reutilized as fuel in cement\nkilns) (MoHUA 2019).\n\nEnergy recovery Gasification of PW is performed via reaction with a gasifying agent (e.g., steam, oxygen, and air) at\nhigh temperatures (approximately 500–1300 °C) to produce\nsynthetic gas or syngas. This can subsequently be utilized\nfor the production of many products, or as fuel to generate electricity, with outputs of a gaseous mixture of carbon\nmonoxide (CO), hydrogen (H2), carbon dioxide (CO2),\nand methane (CH4) via partial oxidation (Heidenreich and\nFoscolo 2015; Saebea et al. 2020). The amount of energy\nderived from this process is affected by the calorific input of\nPW where polyolefins tend to display higher calorific values. Table 3 shows calorific values of various plastic polymers and conventional fuels for comparison. Due to flexibil\nTable 3 The calorific value of popular plastics and conventional fuels\n(Zhang et al. 2021)\n\nFuel Calorific\nvalue (MJ/\nkg)\n\nPolyethylene 43.3–47.7\nPolypropylene 42.6–46.5\nPolystyrene 41.6–43.7\nPolyvinyl chloride 18.0–19.0\nPolyethylene terephthalate 21.6–24.2\nPolyamide 31.4\nPolyurethane foam 31.6\nMethane 53\nGasoline 46\nKerosene 46.5\nPetroleum 42.3\nHeavy oil 42.5\nHousehold plastic solid waste mixture 31.8\n\n\n-----\n\nity, robustness, and advantageous economics, gasification\nalong with pyrolysis is a leading technology for chemical\nrecycling. Characterization of PW is essential for developing optimal process design, particularly for HDPE, LDPE,\nPP, PS, PVC, and PET (Dogu et al. 2021). CSIR-IIP, India\n(Council of Scientific and Industrial Research-Indian Institute of Petroleum) and GAIL, India (Gas Authority of India\nLtd.) in collaboration, have been successful in producing\nfuel and chemicals from PW where PE and PP plastics have\nbeen converted to diesel, petrochemicals, and gasoline. 1 kg\nof these plastics can yield 850 ml of diesel, 500 ml of petrochemicals, and 700 ml of gasoline, along with LPG (CSIRIIP 2018) where the process ensures 100% conversion with\nno toxic emissions and is suitable for both small- and largescale industries (CSIR-IIP 2018).\n\nBiological recycling\n\nBiological recycling or organic recycling involves the breaking of PW with the intervention of microorganisms such as\nbacteria, fungus, or algae to produce biogas (CO2 for aerobic\nprocesses and CH4 for anaerobic processes). PW may be\nrecycled biologically through two methods namely aerobic\ncomposting and anaerobic digestion (Singh and Ruj 2015).\nAn enzymatic approach for biodegradation of PET is considered an economically viable recycling method (Koshti et al.\n2018). Table S1 in the supplementary data shows microorganisms responsible for the PW degradation process which\ncould be utilized in the biological recycling process. Blank\net al. 2020 reported that non-degradable plastics such as\nPET, polyethylene (PE), and polystyrene (PS) can be converted to biodegradable components such as polyhydroxyalkanoates (PHA) using a combination of pyrolysis and\nmicrobiology, which is an unconventional route to a circular\neconomy. Polyaromatic hydrocarbons, polyhydroxy valerate\n(PHV) and polyhydroxyalkanoate (PHH), polylactide (PLA),\nand other aliphatic polyesters are biodegradable, whereas\nmany aromatic polyesters are highly impervious to microbial\nassault (Singh and Ruj 2015). Fig. S3 of supplementary data\nshows an overview of the biodegradation of plastics.\nOxo-degradable plastics which is one of the major classes\nof bioplastics that possess challenges due to rapid breakage\ninto microplastics when conditions (sunlight and oxygen)\nare favorable (Kubowicz and Booth 2017). The behavior of\nspecific polymers interrupts their degradation into monomers due to which the microbial activity is ineffective for\nnon-hydrolyzable manufactured polymers as the activity of\nthe microorganisms responsible for the degradation differs\nconcerning the environmental conditions (Ali et al. 2021).\nOther challenges include the consumption of energy for\nrecycling and time for degradation of the generated microplastics along with socioeconomic challenges such as more\ntime and capital investment and lack of resources (Kubowicz\n\n\nand Booth 2017). Collection and separation of bio-PW and\na lack of effective policy contribute to some other barriers\nrelated to bio-based polymers and recycling.\n\n### Techno‑economic feasibility of different recycling techniques\n\nThe techno-economic feasibility study provides a medium\nto analyze the utilization (raw materials, resources, energy,\netc.) and end-of-life trail for different recovery pathways\nfor the conversion of PW by qualitative and quantitative\napproaches in technical and financial aspects (Briassoulis\net al. 2021a). The association of technical and economic\nprospects of reprocessing technologies and related products’\nmarket tends to have a compelling impact on the formation\nof policies to reduce PW. Hence, the techno-economic feasibility study is essential for the effective management of\nPW. The disparity in melting points and treatment technologies contributes to the major challenge for the recycling of\nmixed/multilayered plastic packaging waste which affects\nthe quality of the recycled product (Larrain et al. 2021).\nTable 4 shows different parameters for techno-economic\nfeasibility for recycling technologies. Though techno-economic feasibility study facilitates the understanding inadequacy prevails in terms of sustainability. This is overcome\nby Techno-Economic Sustainability Analysis (TESA) which\nstudies alternative methods for feedstock alteration, common\nenvironmental criteria (such as mass recovery efficiency, the\nimpact of additives, and emissions from recycling facility),\nand pathways for recycling and end-of-life of plastic products (Briassoulis et al. 2021b).\n\n### Utilization of PW and recycled products in India and contribution of major players toward plastic sustainability\n\nPost-consumer PW can be utilized to produce several products after recycling, such as laying roads, use in cement\nkilns, pavement blocks, tiles, bricks, boards, and clothes.\nDue to good binding properties, when PW is in a hightemperature molten state, it can be utilized in road laying (Rokade 2012). Mixing PP and LDPE in bituminous\nconcrete significantly increases the durability and fatigue\nresistance of roads (Bhattacharya et al. 2018). Various\nindustries based in different locations of the country utilizes PP, HDPE, and LDPE waste plastics to produce reprocessed granules and further use them in the production of\nchairs, benches, dustbins, flowerpots, plastic pellets, mobile\nstands, etc. Few informal recyclers produce eco-friendly\nt-shirts and napkins from PET waste bottles whereas some\nrecyclers convert PW to office accessories, furniture, and\n\n## 1 3\n\n\n-----\n\nTable 4 Techno-economic feasibility parameters for recycling technologies (Briassoulis et al. 2021a; CSE 2021; ElQuliti 2016; Fivga and Dimi-\ntriou 2018; Ghodrat et al. 2019; Larrain et al. 2021; NITI Aayog- UNDP 2021; Singh and Ruj 2015; Volk et al. 2021)\n\nFeasibility parameters Mechanical Chemical Biological for bioplastic\n\n\nTECHNOLOGICAL Type of polymer PET, HDPE, LDPE, PET, PP, PVC, PE, PS,\nlaminated plastics, lowquality mixed plastics\n\nEnergy requirements 300–500 kW/month for 1200–1500 kW for\n30–50 tonnes/month 80–100 kg PW/hour\n(depends on type of technology and polymer type)\n\nTemperature requirement 100–250 °C Pyrolysis—300–900 °C\nPlasma pyrolysis—1730–9730 °C\nGasification—500–1300 °C\n\n\nBio-PET, bio-PE, bio-PP, etc.\n\n40 TJ–1500 TJ (terajoule)\n\n130–150 °C\n\n\nBiodegradability Non-biodegradable Non-biodegradable Mostly biodegradable (PHA,\nPHV, PHH, PLA)\nRaw materials cost Rs. 6–40/kg Rs. 6–40/kg Rs. 10–30/kg\nECONOMICAL Quality of processed materi- Depending on polymer type Depend on type of technol- High-quality compostable\nals ogy and polymer type bio-polymer\nCost of recyclates Rs. 20–150/kg (depends on Rs. 20–40/l (diesel/fuel) Oxo-degradable plastics—Rs.\ntype of polymers and qual- 90–120/kg Biodegradable\nity of recycled products) films/bags—Rs. 400–500/kg\n\nRecycling facilities in India 7000–10,000 15–25 5–10\n(units)\n\nCost requirements (Operat- 50–60 lakhs/annum 50–65 lakhs for 1 TPD 1–2 crores/annum\ning and capital costs) (tonnes per day) plant\n\n\ndecorative garden items. Recycle India Hyderabad, in 2015,\nbuilt houses, shelter bus stops, and water tanks with PW bottles. Further, under this initiative, thousands of chips packets\nwere weaved into ropes, tied to metal frames, and used to\ncreate dining tables. Shayna Ecounified Ltd., Delhi, with the\nCSIR-National Physical Laboratory, Delhi, converted 340\ntonnes of HDPE, LDPE, and PP waste plastics to 11 lakh\ntiles and has commercialized them to other cities such as\nHyderabad, and companies such as L’Oréal International\nand Tata Motors. Further, few recyclers convert PW such as\nmilk pouches, oil containers, shower curtains, and household plastics to poly-fuel (a mixture of diesel, petrol, etc.).\nFew of them collect PET waste and recycle it into clothes,\nautomotive parts, battery cases, cans, carpets, etc. There are\nseveral other non-government organizations (NGOs), companies, and start-ups that are involved in the recycling of PW\nand its conversion to different types of products, even after\npost-consumer use.\nUsing shredded PW, in 2015–16, the National Rural\nRoad Development Agency laid around 7,500 km of roads\nin India. In 2002, Jambulingam Street in Chennai was constructed as the first plastic road in India (TERI 2018). Plastic\nfibers can replace common steel fibers for reinforcement.\nFire-retardant composites with a wide scope of applications\ncould be developed by blending recycled plastics with fly\nash (TERI 2020). HDPE, PVC, LDPE, PP, and PS have\n\n## 1 3\n\n\nyielded conflicting performance measures, which require\nfurther investigation into the performance of the pavement,\nmethods of improving compatibilization between plastic and\nasphalt, and economic and environmental implications of\nthe process.\nFor the reduction in packing, costs and rising issues\nrelated to PW and packaging, FMCGs (fast-moving consumer goods) industries have teamed up with the Packaging\nAssociation of Clean Environment (PACE), have primarily emphasized immediate benefits including a reduction in\nsize and resource consumption where these changes have\npromoted the usage of flexible packaging and pouches over\nrigid packaging forms. Major FMCG companies like Hindustan Unilever (HUL), Nestlé, and P&G have assured that\nthey will reduce the use of virgin plastics in packaging to\nhalf the amount by the year 2025 (PRI 2021). To promote\nthe utilization of recycled plastics, HUL incorporated recycled PET and recycled HDPE in the manufacturing of personal care products (Condillac and Laul 2020). Other companies like L’Oréal and Henkel had successfully eliminated\nPVC in 2018 along with the reduced use of cellophane to\n5.5% in 2019 and reduction in the utilization of carbon black\npackaging to make carbon-free toilet cleaners, respectively\n(PRI 2021). Beverage companies like PepsiCo, Coca-Cola\nIndia, and Bisleri which use a large quantity of PET bottles,\nhave collaborated with several recyclers to upcycle the PW\n\n\n-----\n\nproducts for the production of new recycled utilities such as\nclothes and bags (Condillac and Laul 2020). Similarly, other\ncompanies like Marico and Dabur are also actively involved\nin reducing the use of virgin plastics in its packaging and for\nthe implementation of a recycling initiative where Marico in\ncollaboration with Big Bazaar is providing incentives to the\ncustomers for dropping their used plastic bottles in the stores\nand Dabur is also competing in the race to become among\nfirst Indian FMCG company to be plastic-free (Condillac and\nLaul 2020). On the other side, apart from taking initiatives\nby various FMCG companies, a lot of efforts is being done\nfor the innovation toward plastic-free packaging materials\nand therefore, Manjushree Technopack (Bengaluru, India)\nlaunched its first plant for the production of post-consumer\nrecycled polymer up to 6000 metric tonnes/year to these\nindustries. Other than this, Packmile, a packaging company\nis producing no plastic alternative such as kraft paper (which\nis biodegradable and recyclable) for Amazon India (Condillac and Laul 2020).\n\n### Role of digitization in PW recycling\n\nAs the amount of waste is increasing by each successive\nyear, technology-driven methods can be established for\ncommunities to reduce, reuse and recycle PW in an ecofriendly manner. In light of this, Recykal (in south Indian\ncity Hyderabad), a digital technology firm developed an\nend-to-end, cloud-based fully automated digital solution\nfor efficient waste management by tracking waste collection\nand promoting recycling of non-biodegradable. Its services\nassist in the formation of a cross-value channel coalition and\nthe connection of various stakeholders such as waste generators (commercial and domestic users), waste collectors,\nand recyclers, assuring that transactions between the organizations with 100% transparency and accessibility (Bhadra\nand Mishra 2021). The quantities of waste received per day\nhave risen from 20 to 30 kg in the months following to over\n10,000 to 15,000 kg recently and offer incentives based on\nthe quality of recycled products (Bhadra and Mishra 2021).\nOne such Android-based application is proposed and developed by Singhal et al. (2021), for efficient collection by pickup or drop facility incorporated in the software. Segregation,\nas well as methods for recycling different types of plastics,\nare also suggested and in return, the users are rewarded with\nthe e-coupons accordingly (Singhal et al. 2021).\nFor improvement in plastic recycling, a variety of techniques have been used and blockchain is one among them,\nand it holds promise for enhancing plastic recycling and the\ncircular economy (CE). A distributed ledger, or blockchain,\nis made up of certain immutable ordered blocks which prove\nto be an excellent approach to commence all of their customers' transactions under the same technology (Khadke et al.\n\n\n2021). One such approach is the introduction of Swachhcoin for the management of household and industrial waste,\nand their conversion into usable high-value recoverable\ngoods such as paper, steel, wood, metals, and electricity\nwith efficient and environmentally friendly technologies\n(Gopalakrishnan and Ramaguru 2019). This is a Decentralised Autonomous Organization (DAO) that is controlled unilaterally via blockchain networks which utilize a combination of techniques such as multi-sensor driven AI to establish\nan incremental and iterative chain that relies on information\ntransferred between multiple ecosystem players, analyzes\nthese inputs, and offers significant recommendations based\non descriptive algorithms which will eventually make the\nsystem entirely self-contained, economical, and profitable\n(Gopalakrishnan and Ramaguru 2019). The purpose of AI in\nthis multi-sensor infrastructure purpose is to limit unpredictability and facilitate efficient and reliable separation by training the system to identify and distinguish them appropriately\n(Chidepatil et al. 2020). Most businesses favor blockchain\ntechnology because of its decentralized architecture and low\ntrading costs along with the associated benefits of accessibility, availability, and tamper-proof structures (Khadke et al.\n2021; Wong et al. 2021).\n\n### Discussion\n\nIndia is a major player in global plastic production and manufacturing. Technology, current infrastructure, and upcoming strategies by the Indian government are combined to\nprovide detailed suggestions for policymakers and researchers in the area of achieving a circular economy. The most\nimportant barrier in Indian PW management is the lack of\nsource segregation of the waste. As in many other countries, mechanical recycling is the leading recycling route for\nIndia’s rigid plastics. The influence of thermomechanical\ndeterioration should be avoided to get high-quality recycled\nmaterial with acceptable characteristics. The development\nof advanced quality measurement techniques for technology\nsuch as nondestructive, cost-effective methods to assess the\nchemical structure and mechanical performance could be\nkey to overcoming the obstructions. For instance, the performance of MR can be partially improved through simple\npackaging design improvements, such as the use of a single polymer instead of a multilayer structure. Furthermore,\nPS and PVC could be replaced with PP for the packaging\nfilm market. There are also issues with depolymerization\nselectivity and activity, ability, and performance trade-offs\nthat may need to be addressed before these methods have\nwide applicability. Based on our assessments, Indian policymakers should consider PET, polyamide 6 (PA 6), thermosetting resins, multilayer plastic packaging, PE, PS, PP,\nand fiber-reinforced composites for chemical recycling.\n\n## 1 3\n\n\n-----\n\nAs chemical recycling is innovation-intensive, assessing\neconomic feasibility is the main challenge for developing\ncountries like India. Overall, PUR, nylon, and PET appear\nmost competitive for chemical recycling. The more problematic mixed waste streams from multilayer packaging could\nbe more suited for pyrolysis along with PE, PP, PS, PTFE\n(polytetrafluoroethylene), PA, and PMMA (poly(methyl\nmethacrylate)). Substantial investment is required for\nhydrocracking which can deal with mixed plastics. Better\nguidance on the correct chemical recycling technology for\neach Indian PW stream may require technology readiness\nlevel (TRL) assessments as proposed by Solis and Silveira\n(2020), which require an increased number of projects and\ndata available on the (chemical) process optimization. Compared to conventional fossil fuel energy sources, PE, PP,\nand PS are the three main polymers with higher calorific\nvalue, making them suitable for energy production. There\nare some challenges, however, with this technology, such\nas the identification of specific optimal biodiesel product\nproperties which can be addressed using techniques such as\nLCA (life cycle assessment) and energy-based analysis. As\nthe practical module of the Indian PW management rules\nexplicitly shows the route to oil production from waste, this\nmay indicate a focus on this technology for the country in\nthe future as chemical recycling accounts for only 0.83%\n(as shown in Fig. 3b) among all the recycling technologies.\nAlthough a relatively high cost is associated with bio-polymers at present, it is expected that production costs will\nreduce due to economies of scale in the coming years. There\nare already numerous bioplastic food packaging materials\nin the market. Since food packaging constitutes a large portion of PW in India, a significant impact could be made for\nthe country if it is switched to more sustainable bio-based\npolymers. In India, the J&K Agro Industries Development\nCorporation Ltd, in collaboration with Earth soul, has\nintroduced the first bioplastic product manufacturing facility, with 960 tonnes per year production capacity whereas\nTruegreen (Ahmedabad) can manufacture 5000 tonnes per\nyear. Some of the major manufacturing plants in India are\nBiotech bags (Tamil Nadu), Ravi Industries (Maharashtra),\nEcolife (Chennai). Recently, plant-based bio-polymer has\nbeen introduced by an Indian company named Hi-Tech\nInternational (Ludhiana) to replace single-use and multi-use\nplastic products such as cups, bottles, and straws, which is\nIndia’s only compostable plastic which implies that plastics\nproduced from this bio-polymer will initiate its degeneration within 3–4 months and can completely disintegrate after\n6 months and also, a biodegradable plastic made is converted\nto carbon dioxide and the remaining constituents transforms\ninto water and biomass (Chowdhary 2021). However, there\nare several challenges associated with this technology.\nImprovements are required to sort bioplastic from other PW\ntypes to avoid waste stream contamination. There is also a\n\n## 1 3\n\n\nneed for optimization of anaerobic digestion parameters to\nensure the complete degradation of these materials. From\nthe Indian perspective, feedstock type with their respective\ninfrastructure availability and interactions between sustainability domains is critical for policymaking issues as most of\nthe recycling sectors are operated by informal sector workers. Commercialization of laboratory-based pyrolysis and\ngasification of bioplastic streams should be developed. Due\nto contaminated collection, there is limited recyclability in\nother PW streams, which should be considered as part of\nbio-based PW management. Though India recycles 60% of\nthe total waste generated and its recycling methods are quite\neffective in solving the problem of increasing PW in India,\nthere are still some major challenges or barriers linked with\nit. For more efficient management of all the PW produced,\nstakeholders need to understand and tackle the challenges\nfaced to curb plastic pollution in the country. Different types\nof recycling technologies have their respective associated\nchallenges and barriers (including technological and social)\nwhich need to be addressed as mentioned in Table S2 of the\nsupplementary data.\nRecycled plastics and the products made from these plastics are often expensive from the virgin plastics and therefore\ncompete for their place in the market. The reason behind this\nis the easy availability of raw materials (which are waste\nfrom the petroleum industry) for the production of virgin\nplastics. Other than this, even after mentioning that 60% of\nthe PW is being recycled, a massive amount of this waste\nis found littered and unrecycled in the environment which\ncontradicts the percentage of recycling as there is a lack of\nrelevant and accurate data for the same. Furthermore, Goods\nand Services Tax (GST) also plays a vital role to build market linkages between recycled and virgin products as the\navailability of recycled products is sporadic, the revenue\nor business model tends to collapse for these products and\naffects the recyclers if the PW is being exported where the\nGST rates decreased to 5% from 18% in 2017 (CSE 2021).\nThe increased input costs due to GST and customs taxes are\nbeing transferred to secondary waste collectors by lowering\nthe cost of recycled plastics. For instance, PET bottles were\nRs. 20/kg before GST came in which decreased to Rs. 12/\nkg after GST imposition, milk packets price varied from Rs\n12/kg to Rs 8/kg and similarly, the cost of HDPE dropped by\n30% post-GST (CSE 2021). With the introduction of GST in\nthe plastic value and supply chain, the informal sectors are\nfacing huge losses due to the availability of scrap at cheaper\ncosts. Therefore, the current GST structure has affected the\nmost fragile and vulnerable section of the plastic supply\nvalue chain.\nEnormous studies have been carried out related to different techniques for recycling for various types of polymers,\nvery limited research is available on the techno-economic\nfeasibility of these technologies and therefore, this could\n\n\n-----\n\nprovide a wide scope for the relevant research in India.\nOther than this feasibility study, there is a broad range of\nopportunities and possibilities to explore and analyze the\ntechnologies in India concerning sustainability (involving\nenvironmental and social parameters) through TESA.\nSeveral published reports claim that India recycles 60% of\nthe total PW generated annually which is the highest among\nother countries such as Germany and Austria with more than\n50% recycling. India’s recycling is mostly contributed by the\ninformal sectors but has not been documented accurately by\nthe governing bodies of the country. Moreover, information\non the recycling rate of 60% varies with different sources\nand creates disparity and ambiguity of the data. As depicted\nin Fig. 3b, India recycles 94.17% of waste plastics through\nmechanical recycling, while 0.93% is chemical or feedstock\nrecycling and 5% for energy recovery and alternative uses\nsuch as making roads, boards, and tiles. Compared with\nchemical recycling, mechanical recycling is the most popular technique due to ease of operation and low-cost expenditure as compared to feedstock or chemical recycling in which\nhigh finances and operational costs are involved along with\nthe lack of availability to ascendable technology. Landfill\ndumping is sometimes favored due to improper segregation\nof waste and ease of operation by agencies employed by\nULBs. Other than mechanical and chemical recycling, bioplastics are the emerging alternative for PW in India but lag\ndue to improper legislation, high cost, and unawareness of\nthe segregation of these types of plastics. This can be facilitated if eco-labeling and a proper coding system are introduced. Though these recycling technologies are widely used\nfor reprocessing the PW, elimination of plastics from the\nenvironment is still a far-fetched dream and merely adds a\nfew more years into the end-of-life of the plastics. Therefore,\nthere is a need for affirmative legislation and strict guidelines for the use of recycled products and the exploration of\nalternatives in different sectors. Active involvement of the\ninformal sectors and inclusive growth can be ensured as their\nlivelihood is dependent on PW.\n\n### Conclusion\n\nThe circular economy is a regenerative model which requires\nthe participation of accountable stakeholders. There should\nbe continuous interaction among stakeholders to share current practices dealing with PW as part of the plastic economy. It was found that there was incomplete and indistinct\nreporting on PW generation from individual states. Information exchange via technology application should eventually\nbe an integral part of the PW management value chain. Thus,\ngeneration estimation is an essential task to set targets for\nresource recovery and recycling, which connects the “global\ncommitment” element of the circular plastic economy and\n\n\nwaste minimization. Being part of the global commitment\nto “reducing, circulating and innovating” under the “plastic pact,” a national target could be set and a mechanism is\ndeveloped. In setting a national target, the “dialogue mechanism” would further invigorate inter-and multidisciplinary\nresearch and policy directions. Consumer behavior is an\nessential task as the end-users share equal responsibilities\nas the producer circular economy. Waste management is\na complex multi-actor-based operational system built on\nknowledge, technologies, and experience from a range of\nsectors, including the informal sector. Indigenous innovation\nand research at a regional scale, such as in Gujarat, Andhra\nPradesh, and Kerala, has set an example of a circular plastic\neconomy and would help in developing a further regional\ncircular plastic economy. Efficient recycling of mixed PW\nis an emerging challenge in the Indian recycling sector. As\nplastic downcycling and recycling is an energy-intensive\nprocess, energy supply from renewable energy sources such\nas solar and wind energy can potentially reduce the CO2\nemissions produced. The recovery and recycling of substantial volumes of PW need emerging technological and\nspecialized equipment, which in turn necessitates a considerable capital investment. Informal sectors being prominent in\nwaste management may be deprived of recognition, technology, and scientific understanding but their skills, knowledge,\nand experience can be utilized in the value chain of plastic\nflow. Also, there is a need to formalize the informal sectors\nwith proper incentivization and other benefits as they play\na major role in plastic flow in India. Additionally, there are\nno policies or rules for the treatment of the residues from the\nresult of recycling technologies and their production units,\nwhich needs to be addressed as the number of waste residues\ndepends on the quantum of waste and technique incorporated. Universities, research organizations, and most importantly, polymer manufacturers and most important policymakers should collaborate in renewable energy integration\nand process optimization.\nFurther detailed assessment using LCA should be performed in this regard to identify the optimized solutions.\nExtended producer responsibility (EPR) and other policy\nmechanisms would be integrated sooner or later; however,\none of the fundamental aspects is being part of the circular economy. Although segmented, it is believed that the\ninformal sector is very innovative, and they could also be\ntechnologically enabled. New app development and PW\ncollection campaigns through digitalization could increase\nnon-contaminated sources of PW. Specific manufacturing\nsectors such as flexible packaging, automobiles, electrical,\nand electronics should look at the plastic problem through\nthe lens of resource efficiency and climate change (CO2 and\nGHGs) perspectives. The sectors should develop innovative solutions so that recycled plastics can be re-circulated\nwithin the sectors where they will be the leading consumer.\n\n## 1 3\n\n\n-----\n\nThough there are a lot of available data on different types\nof recycling of plastics and the state-wise flow of plastics\nthere is no proper information on different types of plastic polymers and their respective flow in the value chain in\ndifferent states/UTs. There is a need for the fortification of\nrecycling different technologies for different polymers and\nfor this purpose, the multi-sensor-based AI and blockchain\ntechnology can prove effective in segregation and recycling\nof the PW in a more environmentally friendly manner which\nshould be implemented in all parts of the country for efficient PW management. Furthermore, the amount of PW can\nonly be controlled by the replacement of new virgin plastics\nand existing plastics with the desired recycled plastics along\nwith citizen sensitization. Overall, for a circular plastic economy in India, there is a necessity for a technology-enabled,\naccountable quality-assured collaborative supply chain of\nvirgin and recycled material.\n\nSupplementary Information The online version contains supplemen-\n[tary material available at https://doi.org/10.1007/s13762-022-04079-x.](https://doi.org/10.1007/s13762-022-04079-x)\n\nAcknowledgments The authors wish to thank all who assisted in con-\nducting this work.\n\nAuthor contributions All the authors contributed to the study concep-\ntion and design. Conceptualization and writing of the draft were done\nby Riya Shanker, Dr. Debishree Khan, Dr. Rumana Hossain, Anirban\nGhose, and Md Tasbirul Islam. The draft was revised and edited by\nKatherine Locock with the supervision of Dr. Heinz Schandl, Dr. Rita\nDhodapkar, and Dr. Veena Sahajwalla. All the authors have read and\napproved the final manuscript.\n\nFunding The authors acknowledge project funding for “India – Aus-\ntralia Industry and Research\nCollaboration for Reducing Plastic Waste” from CSIRO, Australia,\nthrough contract agreement.\n\n#### Declarations\n\nConflict of interest The authors declared that they have no conflict of\ninterest.\n\nEthical approval There is no ethical approval required.\n\n### References\n\nAl-Salem SM, Antelava A, Constantinou A, Manos G, Dutta A (2017)\nA review on thermal and catalytic pyrolysis of plastic solid waste\n[(PSW). J Environ Manag 197:177–198. https://doi.org/10.1016/j.](https://doi.org/10.1016/j.jenvman.2017.03.084)\n[jenvman.2017.03.084](https://doi.org/10.1016/j.jenvman.2017.03.084)\n\nAl-Salem SM, Lettieri P, Baeyens J (2010) The valorization of plastic solid waste (PSW) by primary to quaternary routes: From\nre-use to energy and chemicals. 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J Solid Waste Technol Manag 46(1):123–131.\n[https://doi.org/10.5276/JSWTM/2020.123](https://doi.org/10.5276/JSWTM/2020.123)\n\nUttar Pradesh Pollution Control Board (2021) Annual report 2019–\n2020. Retrieved from [http://uppcb.com/pdf/Plastic-Annual_](http://uppcb.com/pdf/Plastic-Annual_090321.pdf)\n[090321.pdf](http://uppcb.com/pdf/Plastic-Annual_090321.pdf)\n\nUttarakhand Pollution Control Board (2019) Annual report 2018–2019.\nRetrieved from [https://ueppcb.uk.gov.in/files/annual_report_](https://ueppcb.uk.gov.in/files/annual_report_PWM.pdf)\n[PWM.pdf](https://ueppcb.uk.gov.in/files/annual_report_PWM.pdf)\n\nVolk R, Stallkamp C, Steins JJ, Yogish SP, Müller RC, Stapf D, Schultmann F (2021) Techno-economic assessment and comparison of\ndifferent plastic recycling pathways: a German case study. J Ind\n[Ecol. https://doi.org/10.1111/jiec.13145](https://doi.org/10.1111/jiec.13145)\n\nWBCSD (2017) Informal approaches towards a circular economy—\n[learning from the plastics recycling sector in India. https://www.](https://www.sustainable-recycling.org/wp-content/uploads/2017/01/WBCSD_2016_-InformalApproaches.pdf)\n[sustainable-recycling.org/wp-content/uploads/2017/01/WBCSD_](https://www.sustainable-recycling.org/wp-content/uploads/2017/01/WBCSD_2016_-InformalApproaches.pdf)\n[2016_-InformalApproaches.pdf](https://www.sustainable-recycling.org/wp-content/uploads/2017/01/WBCSD_2016_-InformalApproaches.pdf)\n\nWołosiewicz-Głąb M, Pięta P, Sas S, Grabowski Ł (2017) PW depolymerization as a source of energetic heating oils. In: E3S web of\n[conferences, vol 14. EDP Sciences, p 02044. https://doi.org/10.](https://doi.org/10.1051/e3sconf/20171402044)\n[1051/e3sconf/20171402044](https://doi.org/10.1051/e3sconf/20171402044)\n\nWong S, Yeung JKW, Lau YY, So J (2021) Technical sustainability\nof cloud-based blockchain integrated with machine learning for\n[supply chain management. Sustainability 13(15):8270. https://doi.](https://doi.org/10.3390/su13158270)\n[org/10.3390/su13158270](https://doi.org/10.3390/su13158270)\n\nZhang F, Zhao Y, Wang D, Yan M, Zhang J, Zhang P, Chen C (2021)\nCurrent technologies for PW treatment: a review. J Clean Prod\n[282:124523. https://doi.org/10.1016/j.jclepro.2020.124523](https://doi.org/10.1016/j.jclepro.2020.124523)\n\n\n-----\n\n"	Plastic waste recycling: existing Indian scenario and future opportunities	This review article aims to suggest recycling technological options in India and illustrates plastic recycling clusters and reprocessing infrastructure for plastic waste (PW) recycling in India. The study shows that a majority of states in India are engaged in recycling, road construction, and co-processing in cement kilns while reprocessing capabilities among the reprocessors are highest for polypropylene (PP) and polyethylene (PE) polymer materials. This review suggests that there are key opportunities for mechanical recycling, chemical recycling, waste-to-energy approaches, and bio-based polymers as an alternative to deliver impact to India’s PW problem. On the other hand, overall, polyurethane, nylon, and polyethylene terephthalate appear most competitive for chemical recycling. Compared to conventional fossil fuel energy sources, polyethylene (PE), polypropylene (PP), and polystyrene are the three main polymers with higher calorific values suitable for energy production. Also, multi-sensor-based artificial intelligence and blockchain technology and digitization for PW recycling can prove to be the future for India in the waste flow chain and its management. Overall, for a circular plastic economy in India, there is a necessity for a technology-enabled accountable quality-assured collaborative supply chain of virgin and recycled material.	2022.0	2022-04-02 00:00:00	https://www.semanticscholar.org/paper/000523657fe1a5879d72c099f619ea0de4424bff	International Journal of Environmental Science and Technology	True
000548b90449dad8f1aaa3207fa6b77503c1d2a3	"# sensors\n\n_Article_\n## A Distributed and Secure Self-Sovereign-Based Framework for Systems of S(...TRUNCATED)	A Distributed and Secure Self-Sovereign-Based Framework for Systems of Systems	"Security and privacy are among the main challenges in the systems of systems. The distributed ledge(...TRUNCATED)	2023.0	2023-09-01 00:00:00	https://www.semanticscholar.org/paper/000548b90449dad8f1aaa3207fa6b77503c1d2a3	Italian National Conference on Sensors	True
000634d00e45d43a7abbc57c02bea6d663cb9232	"http://www.biomedcentral.com/1471 2105/12/85\n\n## SOFTWARE Open Access\n\n# DecGPU: distributed er(...TRUNCATED)	"DecGPU: distributed error correction on massively parallel graphics processing units using CUDA and(...TRUNCATED)	"BackgroundNext-generation sequencing technologies have led to the high-throughput production of seq(...TRUNCATED)	2011.0	2011-03-29 00:00:00	https://www.semanticscholar.org/paper/000634d00e45d43a7abbc57c02bea6d663cb9232	BMC Bioinformatics	True
000c351ffff4b7379817bf6a9c73c4d3617a1395	"# sensors\n\n_Article_\n### A Proof of Concept of a Mobile Health Application to Support Profession(...TRUNCATED)	"A Proof of Concept of a Mobile Health Application to Support Professionals in a Portuguese Nursing (...TRUNCATED)	"Over the past few years, the rapidly aging population has been posing several challenges to healthc(...TRUNCATED)	2019.0	2019-09-01 00:00:00	https://www.semanticscholar.org/paper/000c351ffff4b7379817bf6a9c73c4d3617a1395	Italian National Conference on Sensors	True
0010110e322b5ed622e9a57ff2aed1b092b3cf9e	"## sustainability\n\n_Article_\n# An Attribute-Based Access Control for IoT Using Blockchain and Sm(...TRUNCATED)	An Attribute-Based Access Control for IoT Using Blockchain and Smart Contracts	"With opportunities brought by the Internet of Things (IoT), it is quite a challenge to maintain con(...TRUNCATED)	2021.0	2021-09-23 00:00:00	https://www.semanticscholar.org/paper/0010110e322b5ed622e9a57ff2aed1b092b3cf9e	Sustainability	True
00112bc246d0ad07bf4c6ce0c2ec39f30c3015ca	"Hindawi\nInternational Journal of Genomics\nVolume 2021, Article ID 3102399, 14 pages\n[https://doi(...TRUNCATED)	"Genome-Wide Analysis of the Auxin/Indoleacetic Acid Gene Family and Response to Indole-3-Acetic Aci(...TRUNCATED)	"Auxin/indoleacetic acid (Aux/IAA) family genes respond to the hormone auxin, which have been implic(...TRUNCATED)	2021.0	2021-10-26 00:00:00	https://www.semanticscholar.org/paper/00112bc246d0ad07bf4c6ce0c2ec39f30c3015ca	International Journal of Genomics	True
00159a43bf50d7133c490a38339afdd626c5a975	"Received August 18, 2020, accepted August 31, 2020, date of publication September 3, 2020, date of (...TRUNCATED)	HPBS: A Hybrid Proxy Based Authentication Scheme in VANETs	"As a part of intelligent transportation, vehicle ad hoc networks (VANETs) have attracted the attent(...TRUNCATED)	2020.0	NaT	https://www.semanticscholar.org/paper/00159a43bf50d7133c490a38339afdd626c5a975	IEEE Access	True
00183d0d30904451be10a8ec7ceb6edf4a8f3637	"# Decentralized Hypothesis Testing in Wireless Sensor Networks in the Presence of Misbehaving Nodes(...TRUNCATED)	Decentralized Hypothesis Testing in Wireless Sensor Networks in the Presence of Misbehaving Nodes		2013.0	NaT	https://www.semanticscholar.org/paper/00183d0d30904451be10a8ec7ceb6edf4a8f3637	IEEE Transactions on Information Forensics and Security	True

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DLT-Scientific-Literature

Paper | GitHub

Dataset Description

Dataset Summary

DLT-Scientific-Literature is a specialized corpus of academic publications focused on Distributed Ledger Technology (DLT). This dataset is part of the larger DLT-Corpus collection, designed to support NLP research, language model development, and innovation studies in the DLT domain.

The dataset contains 37,440 scientific documents with 564 million tokens, spanning publications from 1978 to 2025. All documents are in English and have been filtered for domain relevance using a fine-tuned BERT model.

This dataset is part of the DLT-Corpus collection. For the complete corpus including patents and social media data, see: https://huggingface.co/collections/ExponentialScience/dlt-corpus-68e44e40d4e7a3bd7a224402

Languages

English (en)

Dataset Structure

Data Fields

The dataset includes the following fields for each document:

paperId: Unique identifier from Semantic Scholar
title: Title of the scientific publication
authors: List of authors
year: Publication year
publicationDate: Full publication date
venue: Publication venue (journal, conference, etc.)
publicationVenue: Detailed venue information
publicationTypes: Type of publication (e.g., JournalArticle, Conference)
abstract: Abstract of the publication
text: Full text content in Markdown format
url: URL to the source document
openAccessPdf: Link to open access PDF if available
isOpenAccess: Boolean indicating open access status
fieldsOfStudy: Academic fields associated with the paper
s2FieldsOfStudy: Semantic Scholar's field classifications
references: List of referenced papers
lang: Language code
lang_conf: Confidence score for language detection
tok_len: Token length of the document
total_tokens: Total number of tokens

Data Splits

This is a single corpus without predefined splits. Users should create their own train/validation/test splits based on their specific research needs.

Dataset Creation

Curation Rationale

DLT-Scientific-Literature was created to address the lack of large-scale, domain-specific text corpora for NLP and computational research in the Distributed Ledger Technology field. The dataset enables researchers to:

Develop DLT-specific language models and embeddings
Conduct innovation studies and trend analysis
Perform text mining on cutting-edge DLT research
Study the evolution of concepts and terminology in the field

Source Data

Data Collection

Scientific literature was collected from the Semantic Scholar API using domain-specific queries related to blockchain, distributed ledgers, cryptocurrencies, smart contracts, and related technologies.

Data Processing

The collection process involved:

Query-based retrieval: Using targeted keywords to retrieve relevant publications
PDF parsing: Converting PDF documents to Markdown format
Language detection: Filtering for English-language documents
Length filtering: Removing documents that are too short or too long
Domain relevance filtering: Using a fine-tuned BERT model to ensure documents are relevant to DLT

Personal and Sensitive Information

This dataset contains only publicly available scientific literature. No personal or confidential data is included. Author names and affiliations are retained as they appear in the original publications, as this is standard academic practice.

Considerations for Using the Data

Discussion of Biases

Potential biases include:

Geographic bias: Publications may be skewed toward institutions in certain countries
Language bias: Only English-language publications are included
Temporal bias: More recent years may have disproportionately more publications
Venue bias: Certain journals or conferences may be over-represented
Citation bias: Highly-cited papers may be more likely to be included

Other Known Limitations

Temporal coverage: While the dataset spans 1978-2025, the distribution is uneven with more recent years heavily represented
Access limitations: Some publications may be missing due to access restrictions or API limitations
Quality variation: Academic writing quality and rigor vary across publications
Parsing errors: PDF-to-Markdown conversion may introduce formatting issues in some documents

Additional Information

Dataset Curators

Walter Hernandez Cruz, Peter Devine, Nikhil Vadgama, Paolo Tasca, Jiahua Xu

Licensing Information

Mixed open-access licenses including:

Creative Commons Attribution (CC-BY)
Creative Commons Attribution-ShareAlike (CC-BY-SA)
Creative Commons Zero (CC0)
Other permissive open-access licenses

Individual license information is included in the metadata for each document where available. Users should check the specific license for each document before use.

Citation Information

@misc{hernandez2026dlt-corpus,
      title={DLT-Corpus: A Large-Scale Text Collection for the Distributed Ledger Technology Domain}, 
      author={Walter Hernandez Cruz and Peter Devine and Nikhil Vadgama and Paolo Tasca and Jiahua Xu},
      year={2026},
      eprint={2602.22045},
      archivePrefix={arXiv},
      primaryClass={cs.CL},
      url={https://arxiv.org/abs/2602.22045}, 
}