Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Bitcoin's Security Model Revisited   We revisit the fundamental question of Bitcoin's security against double
spending attacks. While previous work has bounded the probability that a
transaction is reversed, we show that no such guarantee can be effectively
given if the attacker can choose when to launch the attack. Other approaches
that bound the cost of an attack have erred in considering only limited attack
scenarios, and in fact it is easy to show that attacks may not cost the
attacker at all. We therefore provide a different interpretation of the results
presented in previous papers and correct them in several ways. We provide
different notions of the security of transactions that provide guarantees to
different classes of defenders: merchants who regularly receive payments,
miners, and recipients of large one-time payments. We additionally consider an
attack that can be launched against lightweight clients, and show that these
are less secure than their full node counterparts and provide the right
strategy for defenders in this case as well. Our results, overall, improve the
understanding of Bitcoin's security guarantees and provide correct bounds for
those wishing to safely accept transactions.

3
The categories of this paper are: physics
37
The categories of this paper are: supr-con
25
The categories of this paper are: patt-sol
16
The categories of this paper are: stat
22
The categories of this paper are: chao-dyn
13
The categories of this paper are: quant-ph
35
The categories of this paper are: mtrl-th
23
The categories of this paper are: solv-int
20
The categories of this paper are: acc-phys
12
The categories of this paper are: nucl-th
6
The categories of this paper are: astro-ph
7
The categories of this paper are: hep-th
2
The categories of this paper are: math
36
The categories of this paper are: cmp-lg
33
The categories of this paper are: plasm-ph
10
The categories of this paper are: q-bio