text:
How to do Bitcoin transactions, if major Internet connections are broken?
If major Internet connections are broken, what happens to BitCoin transactions?
For example, the Internet connection is broken between three major areas (North America, Europa, and Asia) for a couple of hours, and these three regions become isolated to each other.
Can we still do bitcoin transactions inside these three regions?

Bitcoin would be catastrophically broken under such a scenario. Transactions could accumulate any number of confirmations and then unconfirm if blocks leak from one region to another. Bitcoin fails horribly if you are not either connected to none of the hashing power or connected to most of the hashing power. Anywhere in-between, for extended times, is catastrophe.
This is actually not particularly difficult to fix, but nobody seems particularly interested in fixing it.

This is a loaded questions worthy of numerous doctorate or master theses. Don't know the full answer, but can only speculate. Here is a scenario that should exercise a few cerebral muscles.
If the Blockchain is effectively fractured into the three indicated geographical regions (this will be an "extremely" challenging task taking incredible national resources because of technologies such as The Onion Router), each region will have its own mining capacity. Let's assume the mining capacity is evenly distributed across the three regions, the number of transactions inside each region are comparable, and the mining operations are not impacted.  Then it is likely to take three times as long for a confirmation to occur in each region.  This behavior will continue until the 2016 block difficulty factor corrects itself within each region. For this reason, it is not unreasonable to suspect the likelihood of such a Blockchain fracturing event is likely to take place just prior to a 2016 block factor reset, nominally every two weeks. (Loyd's will probably take note of this point.)
To realign the Blockchain will require a great merge & purge (having complexities and heated debates associated with it that is analogous to merging forked code between communities with different interests) requiring considerable international coordination, probably requiring treaties. The blocks that are purged are essentially revoked. This calls into question the validity of the transactions that will be pruned to support such a great merge.  The odds of rolling back the Blockchain will diminish quickly the longer the Blockchain remains fractured.
If the Blockchain remains fractured, the transactions will be regional.  People with the ability to travel and transport their Bitcoins could then spend their BTCs in one region, again in another, and another - roaming double spend attacks. Thus the intrinsic ledger value of the Bitcoins will diminish accordingly - a sudden inflation if you will.
Each region will need to ensure their ledgers remain within their controlled "security domain" because the other regions will have comparable computing power that could be used for attacking the integrity of another region's Blockchain. To ensure the integrity of regional Blockchains, cross domain solutions (CDS) will be deployed at mining pools that have local supernode images. Supernodes will become protected "critical infrastructure" assets and the sharing of information from them will become highly controlled. Thus, solo mining is likely to end when such an epoch occurs, because few solo miners will not be capable of filtering the non-authorized regional transactions from the authorized ones. (For now, the primary market for CDS is for the exchanges to ensure counterfeit Bitcoins don't enter into their proprietary trading platforms.) Bitcoin clients will be forced to use service provider Bitcoin proxies within regional borders.
In a nutshell, if a great fracture remains, the Bitcoin networks will start to look much more like SIP VoIP P2P networks where endpoints authenticate themselves to proxies, proxies establish trusted peering connections to one another. The mining pools will connect to the proxies. The mining pools will then become the keepers of the defacto regional Blockchain. The transactions architecture will become more centralized, but the ownership and banking of the Bitcoins can remain decentralized. Because of the centralized networking governments will be able to still gather intelligence associated transactions.
The deployment of infrastructure described immediately above will be costly, and will thus raise the burden of cost for adopting other P2P Crypto currencies.


text:
Would this be suitable for Bitcoin mining?
Would 10 Port Mini USB HUB High Speed 2.0 with Power Adapter Black #198 UK (on eBay) be suitable for Bitcoin mining?
I have a new PC, so I don't want to damage the motherboard by using the USB ports constantly.
If this isn't suitable, why and what should I be looking for?

You can't damage your USB ports by using them.

I am using an ASIC miner that gets very hot. Plenty of forums say to use a powered USB hub?

Product recommendations are off topic.

There is no connection between using a USB port, powered or not, and your miner getting hot. Your miner gets hot because it is doing work, see below.
USB powered hubs have the capability to supply a limited amount of power if the device needs it. Devices that have their own power source rarely use power from the hub.
Work requires energy. The way energy works is that all the electricity used by the miner is turned into heat, one way or another. All work also generates heat. Even you.
BTW, what miner are you using?

I am using the Asic miner Block Erupter.

If you mean the USB stick it seems that it is powered by the USB hub, there is nothing wrong with that. A USB device tells the hub how much power it requires and the hub decided if that is acceptable.

Been running 3 ASIC miners on a USB hub (similar to the reference above) 24/7 and for a few months now.  No appreciable change on equipment.  Also, buy a USB fan to cool the equipment.  This is the fan I'm using and its working fine.  USB fan
Good Luck!

Thanks for your help. I have a fan running and the device has stayed completely cool so far, fingers crossed!!

How have you been doing so far? Are you mining solo or part of a pool?

Doing well.  Averaging US$12 to US$20 per month.  Though as the difficulty continues to increase, I will need to buy additional ASIC miners to maintain.  I'm mining through Bitminter (http://www.bitminter.com), been good so far.

source: Stack Exchange

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authors: Константин Носков

sort: votes


text:
Is this a safe method for cold storage?
Here is the method I plan to use for creating a cold storage. I am very new to all this, and have never used Bitcoin before. I am not very technical either. Anyway, here it is:

Create a live-cd with Ubuntu (on a DVD, not install anything on the hard-drive, I assume everything will be deleted once I turn off the system).
Install Armory on Ubuntu, create an encrypted wallet using the client (encryption just in case the wallet files does not delete for some reason when I turn off the OS). I write down the encryption key on paper.
Generate an address for receiving bitcoin, write down the private and public key on paper.
Generate a paper backup for my Armory wallet, write down the root-code to this on a paper using the "create paper backup" feature of Armory.
If I ever want to send any bitcoins from my wallet and address I delete the wallet and address later. I only send bitcoins by generating a send signature using an Armory offline wallet that is temporary installed on a live CD, and activate the send signature with a "watch only" online wallet. The offline-wallet will never and have never touched the Internet.

This way I should be able to always have access to receive and send my bitcoins if I still have the paper where I wrote down wallet encryption key, bitcoin addresses and wallet root code, and don't have to worry about data corruption or other hardware/software problems.
Is this a safe method? I plan to put about US$10000 in Bitcoins in cold storage now, but I just want to hear what you think about it before :)
Sorry for beeing a noob to this. I have read about generating codes offline using bitaddress.org as an HTML file, but I have not heard from enough people checking their code to see if the "random addresses" is pre-generated by some way and not as "random" as one might think.

Good point about checking code to see if they are not pre-generated. Armory could be doing this as well (right), but hopefully others have checked their code enough.

It sounds like a lot of hassle to send bitcoins because you have to re-install you offline armory each time. Also, the fact you're trying to do it on a live CD tells me you likely don't have an air-gapped machine. If you think your wallet won't "touch the Internet" in such a case, think root-kit. I would advise against this.
Instead, get a cheap Raspberry Pi (disable the Ethernet) and use that as your offline wallet. If you encrypt the wallet and generate your paper backup, your coins will be very safe, (provided you don't lose your paper backup) and will be less of a headache to access your funds.

I agree absolutely.  Well done

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text:
Can I use run Bitcoin Core in regtest mode in v0.8.1?
I'm trying to run bitcoin-core v0.8.1 in regtest mode, but it doesn't work.
When placing regtest=1 in bitcoin.conf it starts to sync the mainnet.
I've not seen anything related in the code.
So I was wondering if there's any configuration different to run regtest mode in that version different from more recent ones.
When was regtest mode added ?

May I ask why you're interested in using such an old version? Depending on your goal, another approach may be better.

Sure!
I'm making some tests with the disabled opcodes re-enabling them again. And realised that the 0.8.1 was the last version where them were coded, so it was easy to "enable" them. I just coded the bitwise logic ones in the current version, but the arithmetic ones were difficult, so i tried to run the 0.8.1.

Regtest mode was introduced in version 0.9.0, via pull request #2632. That is why it doesn't work in 0.8.1, as you noticed. There is no other option to run regtest in that version, although testnet3 is supported by that version so you should still be able to use that if it suits your needs. Otherwise just upgrade to a newer version which will contain performance improvements, bugfixes and newer feature support :)

Oh.. okay!
I was trying to do some tests with some code that was removed from the core, and that was the newest version including the code.
For other tests i'm using v0.15.1 in regtest and testnet too, depending the necessities.
Thanks!


text:
Help please recovering a wallet from a 17 word mnemonic phrase and other info
4 years ago I bought bitcoin and I have
a 17 word mnemonic phrase
an identifier
a bitcoin address
and what I believe is a password
Does anyone know how I can access this bitcoin?

You can verify that it is in fact the blockchain.info wallet by seeing if all your words are on their wordlist: https://gist.github.com/fulldecent/fa6a223ab4adb7672bba4a6653cd1b0e

Do you remember where you created the wallet?
I assume it was a legacy wallet on blockchain.info, if so you can recover your ID and password here https://blockchain.info/wallet/forgot-password .

ah ha...by George I think that's it.  I couldn't log in using my pc so I tried using my tablet and got in.  thank you for the assist

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text:
Is the Bitcoin Diamond wallet website bcdwallet.org legit?
I am looking forward to using BCD and I found a wallet that is giving away 1 Bitcoin Diamond if I verify my BTC wallet, should I trust it?
It is at bcdwallet.org

This is malware.

Anything that sounds too good to be true likely is.  I wouldn't trust it just on the face of offer of a "free" BCD.

If the site in question is a scam, this question provides important information for the community, so it makes more sense to upvote this question than downvote it.

Why downvote it? The question is genuine! You're voting on question, not the website.

No, bcdwallet.org is not legit; it will just steal your bitcoins.
Because the website is asking for a Bitcoin wallet seed, which can be used by them to immediately steal your bitcoins, it's almost certainly a scam.
When I do a search for the website in Google, there are very few results, so it doesn't have any good reputation to speak of.
The domain name uses name servers based in Russia, and the domain Registrant details are hidden, so that adds to the likelihood of it being a scam. The domain was registered on 2017-11-26 (only 2-3 days ago). A very recently registered domain name is another hallmark of it being set up just to steal your money.


text:
P2SH-P2WPKH private key or revert to P2WPKH
Is there a way to get the private key out of an P2SH-P2WPKH address, using Bitcoin Core 0.15.1?
If not, is there a way to get the origin P2WPKH address to get the private key out of this address?

You can't go from a public key to a private key, segwit or no.

I have the addresses in my wallet. It's not from a public key.

What wallet software are you using?

0.15.1 bitcoin core

In 0.15.1 you'll need to find the P2PKH address corresponding to the key (it's the argument to addwitnessaddress you used for creating the address in the first place), and pass that to dumpprivkey.
In 0.16, things will likely just work.

using listreceivedbyaddress makes it possible! Thanks

I'm confused! How does that RPC help you?


text:
Where can I create a bitcoin address?
I wish to start mining but I could not since I do not have a bitcoin address. Where can I create this address?

You can use https://www.bitaddress.org
It is an interesting, lightweight, trustable and really easy to use solution.

You can create safe bitcoin address from :

Your pc
Blockchain.info
Cex.io
Just-dice.com
Btc-e.com

If you do not have bitcoin-qt installed you can sign up on www.blockchain.info to acquire a bitcoin address


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How to get full Block information like blockchain?
How to get these values?

Output Total
Estimated Transaction Volume
Transaction Fees
Relayed by

Raw blocks are available at datafolder/block/blkXXXXX.dat in serialized in network format or can be downloaded from the p2p network.
As you can see in the format, each block has a list of transactions which in turn has a list of outputs. If you sum each output value, you get the output total.
The estimated transaction volume is calculated like the output total, but not counting the change outputs. There's no reliable way to know which output is being sent and which one is change, so you'll have to guess, take the mean or something like that.
One of these transactions must be coinbase. A coinbase transaction has a single input with txid = 0000000000000000000000000000000000000000000000000000000000000000. If you sum all input values (not including coinbase) and subtract all output values (again, not including coinbase) you get the total fees. Inputs don't have a value, so you have to find the transaction they're referring to (txid) in a previous block and the referenced output in that transaction (vout). There's a cheap (but not reliable) way to calculate the total fees. Just sum the coinbase outputs and subtract the block reward. The value is only accurate if the miner claimed the whole reward and fees (which is not enforced anywhere).
You might have noticed the relayed by is nowhere to be found. This is different for everyone, and is only the client which sent you the block for the first time. To know who relayed the block to you, you have to set a client listening for block broadcasts and just record whoever did broadcast the block to you.


text:
What is the difference between a wallet and paired keys?
So I've read that a wallet is basically a public address key paired with a private key.
But is it more than that?   Does the physical wallet file contain transaction and balance information as well or does that get pulled from the cloud?
For example, let's assume I have just the public and private keys written down on a piece of paper...
If I import those keys into a wallet client, will the wallet client download my balance and transaction history associated with my address from the cloud?

Yes. The cloud you're referring to is actually the block chain. A bitcoin wallet has various different meanings, such as web-wallet, brain wallet, or various others, but in my opinion the best representation of a wallet is actually a file, commonly a wallet.dat file. Then you use a bitcoin client to open this wallet file.
Inside this file there's various key pairs that you can use to make bitcoins transactions. No balance information is kept in this file otherwise it would be extremely large in size.
The important part is that a bitcoin wallet's format is not standardized. This means that each bitcoin client implements its own wallet file format. You can't import Bitcoin-QT's wallet file in Multibit for example.
But again, a wallet can be represented in a variety of different ways: as files, on the web managed by third parties, as a piece of paper, etc.

But what else exists in the wallet file aside from the public/private key?  Just transaction data that can be redownloaded easily from the block chain?  Is the private/public key the only thing important to backup?

@sayguh check this page http://bitcoin.stackexchange.com/questions/853/what-do-the-different-dat-files-contain?rq=1


text:
Is there a US broker for Bitcoins?
Apparently, there is an Australian trading house, Bit Trade, that will trade currency for Bitcoins or vice versa.
Is there a U.S. equivalent?

There is indeed a US Broker for Bitcoins.  Unfortunately, for now, they're still in private beta.  The company is called Buttercoin: https://www.buttercoin.com/  You can sign up for their private beta, but there's a pretty long waiting list right now.

Whoever downvoted this has a valid point since this isn't helpful yet.  At the moment, your best bet as an alternative would be either trading OTC with bitcoin-otc (See http://bitcoin.stackexchange.com/questions/1829/how-does-one-use-bitcoin-otc?rq=1) if you're technically minded, or trading on Localbitcoins.com if you're comfortable doing the trade in person.


text:
Bitcoind, what's the command to see available funds?
Bitcoind, what is the command to see how many btc is available combined in all wallets?

Related: How to get an address's balance with the bitcoin client?

It is not clear to me whether you are asking for the global unspent transaction outputs or the user's balance.

bitcoind getinfo
The Bitcoin daemon supports just one wallet, not multiple.

Then what about wallet addresses. Aren't those wallets.

A wallet is not an address. An address is not a wallet. I answered the question you asked.


text:
Why is it insufficient funds when sending coins via datacoind when I have enough?
I'm trying to send my coins from my daemon I installed in my server. Its datacoind, but I'm guessing its the same as bitcoind. Is that a correct assumption?
http://prntscr.com/2h4eex
root@x:~# datacoind listaccounts
{
    "" : 11.43010363,
    "pat" : 0.00000000,
    "pats" : -0.45000000
}
root@x:~# datacoind sendtoaddress DJKrNvrnuuTsvuwThYfjP2Mo 7 "testing this out"
error: {"code":-4,"message":"Insufficient funds"}
root@x:~#

Off-topic because it's specific to a non-Bitcoin altcoin. Bitcoin won't behave like that.

I disagree, it is the only stackexchange for cryptocurrency that has any people with extensive knowledge
EDIT What is your transaction fee set at

Crypto currencies other than Bitcoin are still on topic here. See the help center. However, it might help if you can provide some more info about datacoin, for those who may be less familiar.

if you want to read up on datacoin: www.datacoin.info --- its a new coin that came out about a month ago where you can attach upto 128KB worth of data to each transaction. thereby creating a decentralized cloud storage. a potential game changer i must say.


text:
Which wallet applications implement BIP38 - Private Key password encryption
I just learned about bip38 as it has to do with bitcoin private key encryption by putting a password to the key on the QR code. My question is which wallet apps support this decryption feature?

See:
What is the current state of BIP 38 (encrypted paper wallet) integration with cell phone wallets?

Bip38 QR password protection can be read by block chain.info wallets and on android it can be read by the mycellium wallet app. It will pop up a enter your password dialog box once you scan it.

The paper wallet generator from Bitaddress lets you encrypt with BIP38.

but how do you decrypt it?

That's on the same page: click the tab "wallet details", enter the encrypted private key, press view details, enter the BIP38 passphrase, and finally click decrypt BIP38.

i guess we'll have to wait until someone implements it into an application as no way is anyone going to type out a case sensitive private key! =)

There are ways of copy-pasting it. On bitaddress, use "hide art" to copy the private key.


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What is the definition of a P2P exchange?
Bitcointalk member BTCLuke suggested the following six criterion for a P2P Exchange:
A P2P Distributed Exchange MUST:

Be without any central points of failure, since a government or two WILL be coming after it one day. I suggest a Bitorrent-like software schematic.
Show everyone a very large number of possible trades to choose from, (thousands?) so assets can form a stable price. (e.g. a Bitcoin is going for $120)
Transact trades pretty much INSTANTANEOUSLY, so when you're watching a graph and want to trade at a very specific time you can do so. (This is extremely important for arbitragers and other traders who help keep the price fluctuation down.)
Offer Graphs and APIs for for graphing like MtGox does.
Have three-user (trustless) trading, so a non-interested 3rd party always hosts the trade between the buyer and seller. (And should provide Escrow too!)
Hold and transfer IOUs without the need for trust

Does there exist a whitepaper or open sourced project that has a solution for all six criterion? Furthermore, who in the community has been working on P2P exchanges and what regulations would impact them?

6 is silly. When you have $50,000 in the bank, that's value. Sure, it has a risk discount because the bank might go out of business. But it also has a convenience premium because the bank makes possible things like electronic banking, provides security, and so on. To argue that an IOU is not value is, frankly, just bizarre.

Maybe if a certain lead cryptographer on a certain project would be willing to record a lecture for the bitcoin education project one could escrew all these bizarre notions of IOUs....Just saying David, we'd really like to have you.

6 is totally and utterly silly, mostly because either you are teleporting cash, or you are trading IOUs. Pick one or the other.

I'd say 1 & 3 are the only required ones.

Decentralized peer to peer exchange of digital currencies to/from fiat currencies will always have the following constraints:

Fiat currencies cannot be encrypted and represented digitally by a decentralized entity/organization/system. Therefore, fiat currencies will always need to be transferred between traders through the banking system or physically using cash.

Peer to peer trades of fiat<=>digital currencies will always depend on trust. A peer to peer exchange protocol could easily ensure that one party would always send the Bitcoins. The transaction can be verified. The protocol could safely hold the Bitcoins until the other party sends the dollar (Decentralized escrow). But the protocol can never confirm the dollar transaction. It can never know for sure that the transaction has occurred. This introduces the below:

Who's going to send first?
I sent the money. No he didn't
Who will this person be that I'll receive a transfer from? Is he a criminal? Are the funds stolen?
What if this person tells his bank that I fraudulently received this payment.
I went to the cash exchange and had to confirm the transaction at gun point

Remember that transactions  within the banking system are monitored, they can be reversed and funds can be frozen.
I have studied all projects aiming to accomplish a peer to peer decentralized exchange:

Dark Exchange
BitcoinX
Ripple - which is actually a payment system that will hypothetically allow trades as well.

I haven't seen a solution for the above mentioned constraints. All of these projects will be bound by them.
Ripple protocol proposes to allow dollars to be represented on the network and allow peer to peer transfer of dollars, therefore enabling btc->dollar trades. However, their model depends on Gateways -the entry/exit points of fiat currencies to the network. Users will still need to trust that these Gateways will actually hold and be able to pay the amount of dollars within the network as/when needed. There is no guarantee that these Gateways will not fraud the network or individuals. Neither is there a guarantee that the governments will not shut them down. (Read the first line here: https://ripple.com/wiki/Gateway_List)
My view on the future of fiat=>dollar exchanges:
First and foremost: The significance of exchanges will diminish as the adoption of Bitcoin grows. The less the need to trade your Bitcoins, the less important exchanges are. I truly believe this.
Are you saying that we not need exchanges? Absolutely not. No matter how much the adoption rate grows, there will always be a need to trade Bitcoins -this will be true for at least our  lifetime. So we need better and more exchanges.
So what's it gonna be? A ton of local options for people to buy/sell Bitcoins and lots of big exchanges that local shops can trade with. You need to remember that currency exchange does not always have to be in continuous double auction format. When you go to an exchange office and buy euros with dollar, they are not actually matching that with another order. They put a safe profit margin on the price and we pay it. See: CoinBase
Overall, I truly hope that I'm proven wrong. But I don't think a peer to peer decentralized exchange can be built.
Important last note: All of the above are true only for fiat to Bitcoin exchanges. A digital to digital currency exchange can be made peer to peer and decentralized given that both allow peer to peer public transfers and both are decentralized. (Ex. Litecoin to Bitcoin)

Great answer, especially the point about fiat to digital exchanges always requiring trust. See my answer for a model that tries to solve the problem of trust.

Could you expand on your "Important last note"?

I don't know how it can be done but peer to peer exchange of crypto currencies with a public ledger should be possible. At least in theory.

@Randomblue I believe the key word is "atomic" chain-chain transactions.

Ripple is centralized. It is backed by a company that can be shut down by a government.

@jiggunjer yep, atomic swaps are how crypto to crypto exchange is made possible today with segwit. The tech didn't exist in 2013.

I think the best we have as a P2P exchange is Ripple. Citing their website:

Ripple is a payment system for any currency with support for
  cross-currency transactions. You can use Ripple to send and receive
  money in dollars, euros, yen or Bitcoin without having to do extra
  work for foreign exchange transactions. Now, you can spend and receive
  your Bitcoin as easily as any fiat currency.

So, Ripple can be used as an exchange for different currencies.
However, it does not comply with all the requirements you listed. Let me go over them.

Be without any central points of failure, since a government or two WILL be coming after it one day. I suggest a Bitorrent-like software schematic.
Ripple itself has no central point of failure if their intended network topology is followed. However, for exchanging currencies, Ripple still depends on gateways that do the actual exchange. Still, these gateways need only to be trusted for a limited amount of currency. If you would really want to, you could see them as the trackers in BitTorrent's paradigm.
Show everyone a very large number of possible trades to choose from, (thousands?) so assets can form a stable price. (e.g. a Bitcoin is going for $120)
In Ripple, all trades happen through gateways. So for every gateway you could have an order book. Probably it's more useful if every gateway just shows its current exchange rate and trade volume. For a more detailed market depth, you will probably be referred to the gateway's website.
Transact trades pretty much INSTANTANEOUSLY, so when you're watching a graph and want to trade at a very specific time you can do so. (This is extremely important for arbitragers and other traders who help keep the price fluctuation down.)
As far as I know, things in Ripple itself are instantaneous. Exchange delays will most probably end up being very gateway-specific.
Offer Graphs and APIs for for graphing like MtGox does.
This is an interesting one. I don't think Ripple currently supports exchanges via gateways. But Ripple is really still very immature (the server code isn't even released yet), so it is very much possible that this is coming.
Since most open software tries to make it possible to do the exact same thing via the API as you can do by using the software itself, this will most probably come to the API.
Have three-user (trustless) trading, so a non-interested 3rd party always hosts the trade between the buyer and seller. (And should provide Escrow too!)
Ripple plans to support escrow. Whether that will apply to XRP transactions as well as gateway exchanges is unsure to me.
Hold and transfer IOUs without the need for trust
Since the whole thing Ripple is built upon is trust, I think it just fails this one. It can hold IOU's though, in fact that's basically all it does.

So, I know Ripple is not the ideal solution you were looking for. But still, Ripple is very much about exchange of currencies, so maybe some day it will be suitable as a true P2P-like exchange.
(Also, I'm no Ripple expert. Feel free to correct me if I made a mistake!)

Concerning "2." I thought every user in the ripple network could offer to exchange assets.

Note that Ripple is not yet fully decentralized. There is still at least one component (the UNL) which is maintained by a central authority (Ripple themselves). There is a roadmap for making UNLs decentralized so to be seen how that pans out.

Check this suggestion from a member of Open Transactions using Bitmessage for trust-less decentralized exchange system
https://bitcointalk.org/index.php?topic=212490.0

Just a link on 10+ pages thread on a forum is not the best answer. Could you please outline how those six criterion are fulfilled by a combination of Open Transactions and Bitmessage?

A good answer should describe the content of the link. Links go dead.

Look for Open Transactions and Bitmessage... But I think it is still theory. https://github.com/Coinffeine/coinffeine is more code now rather than only words and theory.

The marked answer covers most of the major concerns I would have but there is one idea I've seen that does have some merit.
The crux of the challenge is that a decentralized exchange requires you to trust someone with your fiat.
In Ripple and Bitcoin – Foundations of a Decentralized Economy they describe a model I would trust for small amounts of fiat.
The basic idea is you establish lines of credit with people you trust.
A simple scenario is when the two people wanting to make a transaction have a person in common who they trust. Paraphrased from the article:

Mark and Brian are strangers who want to make an exchange. Mark is willing to sell 0.5 BTC to Brian in exchange for $50 (USD).
Brian has previously established a line of credit with his friend John for up to $100.
And John happens to live with and be friends with Mark and they also have agreed to trust each other for up to $100 of credit.
So once John has been notified that the transaction is valid he pulls out his wallet and pays Mark the $50.
Brian now owes John $50 and since they trust each other they can sort that out when and as they wish.

A picture (source: Ripple) might help.

This can easily be extended to chains of trust so that a person in common isn't needed.
I still have a couple of small concerns with this model:

Collecting for larger amounts could be a burden and not very timely since it would be spread across a large number of your trusted friends.
There is some risk with your total debt obligation to friends. It would be rare, but if you agree to give a credit line to 100 friends, each for $50 and the majority of them need to draw on that in the same week you would need to come up with something approaching $5000 in cash. The system would need to include a "max amount per day / week / month" that you would be willing to cover.
Chasing friends for the cash they owe you could get very annoying. It would have to be automated somehow for it to be practical.

But it seems like the minor concerns I have could be addressed in an automated way, so I think this model has some promise. Now Ripple just needs to finish decentralizing the still centralized elements of their network (the UNLs for example as explained in this question) and this model could have some potential. In aggregate, I actually trust my friends far more than I trust my bank.

Since you asked for a definition, the most naive version of a p2p exchange just needs to allow buyers to meet sellers and vice versa, e.g. via a broadcasting mechanism. All else is optimization, which is important to minimize fraud/loss and maximize ease of use.
These optimizations can have many forms also depend on if the type of transaction is pure crypto-crypto or the hybrid fiat-crypto.
One popular mechanism for securing hybrid transactions is using 3rd party arbitrators in a multi-sig transaction. Another option is to use tokens (another crypto) that are fiat-guaranteed by a third party (e.g. a group of companies called Gateways). Either way you need to pay the third party for their service.
Pure C-C transactions could exclude third parties but have their own technical challenges.
The theoretical advantage of matching peers (P2P) is that market efficiency will balance the buy/sell prices in a fair way, and if enough peers join there could be a single exchange value since the margins from both parties offset each other.
I don't like the terms centralized vs decentralized because p2p isn't inherently decentralized. You could have a centralized (hub) system that matches peers, likewise you could have a traditional 'consumer-to-business'(C2B) exchange that runs on a decentralized network.

Cryptobridge https://crypto-bridge.org/ is a brand new decentralized exchange built on top of bitshares, but with more gateways.

The blockchain behind the decentralized exchange, graphene, can process up to 100.000 transactions per second and has an average confirmation time of just 3 seconds.
Each client holds the private keys to their coins. CryptoBridge has no access to the client's funds.
There is no central point of failure. All deposits, withdrawals and all order books are transparently stored on the blockchain.
You can also stake BCO (Bridge Coin) and earn money from every trade made on the platform.


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Where does the change go in blockchain.info when using a paper wallet?
When using a paper wallet as watch only  via block chain.info and you send partial amounts out from it. Where does the change go?
I've read you can lose all your coins if the client doesn't handle change properly. What's a scenario that could lead that to happen? Which apps don't handle change properly?

(I assume here that you have a simple single-address paper wallet, like the ones from BitAddress.org. I also seem to have understood that you use the Blockchain.info app to make the payment.)
You should be able to decide yourself where the change goes (using the web-apps's Custom Send feature), but Blockchain.info's default behaviour is to send it back to the original address.
Especially if you have a paper wallet with only one address, Blockchain.info won't generate new change addresses for you.
So this is what happens:

Let's say you received two transactions on your paper wallet. One for 2 BTC and one for 3 BTC. When you try to send 1 BTC to someone, the Blockchain.info app will:

Take an output that has at least 1 BTC. This can be done randomly, but I suppose it will take the oldest one. If you don't have an output large enough, it will combine multiple ones until they have at least 1 BTC all together. Suppose the 3 BTC output is chosen.
It will make a new transaction with the 3 BTC as input. It will create an output for the 1 BTC you want to send to another address. It will then have to specify what to do with the other 2 BTC.
Considering that it only knows about one of your addresses, it will use this address for change. This means an additional output is created for 2 BTC, sending them (back) to your paper wallet address. (Note that Blockchain.info charges the minimal transaction fee by default, so this will be deducted from the 2 BTC change.)

So basically, you don't have to fear for losing your coins. And you will be able to spend the change from your paper wallet automatically.
However! This type of use, is not what paper wallets are intended for. Using Bitcoin, you are supposed to use a new address for every transaction. This is to ensure your privacy. When you use your paper wallet like this, everyone you ever made a transaction to or that ever made one to you will know your balance. This is obviously not what you want. Paper wallets are originally intended to store an amount of coins safely offline. When you want to use them again, your privacy ensured only if you send them back to a regular wallet that uses change addresses like it is supposed to.

thank you for really clearing this up. as it was quite scary to move BTC around and finding out that their are change addresses involved. currently i dont really care about the privacy issue as its not like i have alot of btc and it would require extra paper wallets everytime i just want to take out a few mbtc to spend. im just using paper wallets as my safe deposit box. it seems safer than having it loaded on a computer which is prone to malicious software.

@duckx Well using it as a safety deposit box is a good practice. But please be careful, I made the assumption that you use the Blockchain.info app, who has this behaviour. When you use other wallet apps (like Miltibit as Raghuram suggested), other things may happen regarding change addresses.)

yea i mainly use the blockchain.info app. the thing is that i feel like it gives it another layer of security if blockchain.info ever goes down, you still have the paperwallet on hand.

This is an excellent answer and I would only change 1 character. I've raised a discussion to see if this is possible.

I explain my recent experience with paper wallet. This might be helpful.
I generated a paper wallet from coinbase and securely stored its private key in cloud. I also used blockchain.info to monitor the balance using the public key only (no private key is entered). And recently, I wanted to transfer few bitcoins from it to sell. I knew that if I import the private key in coinbase.com, it sweeps all the coins from that address and transfers all of them to a new address whose private key is managed by coinbase. Blockchain allows to import private key without sweep, but I did not want third parties to learn about my private key. So I thought of using Multibit client. I installed multibit client, exported all its private keys to a file, and added my private key to the end of the file and imported back. I see all my coins in multibit (1.6 BTC). So far good. Now I transferred, 0.5BTC to coinbase to sell them and multibit showed the balance as 1.1BTC, which is correct. But the watch only address in the blockchain started showing only 0.6. I got confused as the balance I expected was 1.1. So I carefully monitored the transaction and found that 0.5BTC was sent to my coinbase address and another 0.5 was sent to one more address which I didn't recognize. As multibit was still showing the correct balance I guessed that it might be one of the multibit address and I actually found it there. So, multibit actually took coins from my paper wallet address and put it in an address that was generated by multibit, which I did not expect. I was planning to use multibit only as a temporary solution and was planning to uninstall it after I transfer my BTC to coinbase. If I was not careful then I would have uninstalled multibit and deleted the wallet. Now I learnt how multibit works now, and I am not sure why it does like that. But a lesson learnt.

thanks for the heads up. this is something everyone needs to know about.

This depends entirely on the program used to send the bitcoins.  It may use pregenerated change addresses specified on the paper wallet, or it may send it back to an address of the paper wallet itself, or generate a new address.  If the latter, you have to be sure to also print out the private key of this new change address.
In the most likely case, the software will create a new change address or use a change address not associated with the paper wallet, and you will have to print out a new paper wallet for the change address.

but how would u even know if there was a change address when using a paper wallet that was printed out from bitaddress.org?

Unless the software is specifically written otherwise (and the paper wallet be generated specifically for that software), it wouldn't contain your change address.  When making a transaction, you will need to print out a new paper wallet for your change address.

so what your saying is when spending from a paper wallet and you don't have a paper change address preprinted out your change will go to some random address in the application? which application does this?

All I'm saying is that the behaviour depends on the client.  Regardless of which client, you'll have to look at which address it's changing to and probably export and print the change address as another paper wallet, or use an address that you have already printed out as your change address.


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Why coinbase doesn't address callback?
I am using PHP cURL to generate new address from coinbase. As per this documentation we get notification on the callback url when any transaction is made on the generated address. But I am not getting any callback from coinbase when I receive any payment.
I want to achieve the following:

Generate a bitcoin address
Store the the generated address & the amount with it's user who paid it.

I am facing the problem in getting callback. I get payment in the coinbase & email saying that you received this amount etc., but no callbacks.
Also please suggest me that whether the coinbase is secure or not.
If not, what should I go for? I want to get the above things done.

Give your website address in Merchant Settings then check by clicking Test


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Multibit security — How anonymous is it?
Hi and I hope someone here can answer these security questions for me.
I have downloaded the Multibit client onto both a windows laptop and also a separate download onto a laptop running ubuntu linux.
My questions are for both operating systems and they are:

When I am online and start the Multibit client is my IP address broadcast at anytime when I am using it such as when it syncs with the BTC network?
If I create say 10 wallets in the client and issue one receiving address from each wallet to ten different people so they can pay me, is it possible to see that all those addresses and wallets reside within the same Multibit client?
Can those addresses or wallets be traced back to either of my laptops and if so how can I stop this from happening?

Something else to consider is what you then do with the money. For example, if you send the money in those 10 wallets to one address, the blockchain will reveal that those 10 wallets have some association (possibly the same owner). If you have a transaction that sends money from more than one of those accounts at once, that makes it clear that there's an even closer association (probably the same owner).

I think what you are asking is this:
Because Multibit is a lightweight SPV wallet, it uses Bloom filters to request the status of its own wallets from other peers rather than collecting the latest blocks.
Could those other peers, who already know the IP address, conclude that the request for information concerning certain addresses imply that this IP address is looking after these addresses?
The answer would be yes it could conclude this, but it could never say for sure if the private keys were also owned at that IP address it could only assume this.
The matter is further complicated because connection to peers is fairly random according to their availability.
EDIT I am updating my reply, as it appears that some research has been carried out which may contradict what was thought to be the case, but this is not strictly related to Multibit, but all wallets that use internet protocol. The Coindesk article points to the paper:
"Eavesdropping" attack

No, your IP address is not "broadcast". It is used when communicating to the peers that your Bitcoin client chooses (usually about 8 others).
No, there is no information encoded into addresses that reveals which ones are associated with others. A Bitcoin address can be considered to be a purely random number.
No, there is no evidence that an address is associated with a particular IP address. Your client will send new transactions to its peers, but the receiver won't be able to tell whether your client originated the transaction or whether it was relayed from somewhere else.


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What is the equivalent of cold storage or paper wallet for NXT?
I want to be able to secure my NXT in cold storage. What are some ways of doing this?
Since NXT is only accessible via a brain wallet, I can just store the passphrase on a paper, but what if I wanted to see it as a watch-only address? Is that even possible?

It is possible, but quite more difficult than with Bitcoin.
All NXT tokens/coins are stored on the network, but it is possible to create an account "offline" that is secured by a 256-bit public key and does not expose your private key to the network.
There is a step-by-step tutorial on the NXT-Forum.

so your saying you can just generate an address with an offline computer even though the blockchain isnt even downloaded? but dont you have to go online to send a transaction in order to secure it better with 256bit encryption?

I'm no expert in nxt but the tutoria seems pretty decent so try it out ;)


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I'm mainly on a Windows system. What are some advantages and disadvantages of setting up Bitcoin-Qt in a Linux virtual machine?
I'm on Windows. Would it be a good idea to load up Bitcoin-Qt in a virtual machine running Ubuntu? What are some disadvantages I might run into?
I was thinking it would be secure as everything is in the virtual machine, and I can easily copy that virtual machine out to another computer if it ever crashed.
I also plan to run other crypto currencies as well.

Duckx, I think you have a good idea.
Well for one thing -- using a linux VM is much better for security.
You are essentially using your windows machine for browsing the internet / email and your linux machine for only bitcoin banking.
All it takes is someone to compromise a bitcoin related website and you could be out of your bitcoin holdings.  With your wallet.dat running in a Linux VM if someone compromises your windows machine they won't be able to easily steal your wallet.dat and keylog your password, etc.
If you're not using the Linux VM for Bitcoin banking, you can have it turned off!
It's trivial to encrypt your entire linux HD.
Linux is inherently more secure out of the box than Windows, and with a few tweaks, extremely secure.
Technically though, if someone compromises your Windows machine they could gain control of your vm and get to your bitcoin assets.  This type of attack though is extremely rare and would have to be personally targeted rather than some worm looking for wallet.dat files.
Almost all major Bitcoin applications are developed on linux/osx so you will be in good shape.
As for a performance hit... you won't even notice it.  Linux doesn't take much overhead to run at all.
Finally, when you transfer the BTC to your linux machine, do not transfer the wallet.dat just create a new wallet on the VM and send your BTC/LTC whatever via the network.  This way you don't have an unsecured copy that could be stolen.

There shouldn't be any problem.
But I think it is a waste of memory/disk/processor time. You may just store the blockchain on some external drive, if you want that to be portable.


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How do I trade dogecoin for money?
I have read a lot about how to build and tune hardware for script mining, but it is still unclear to me how to trade what you have produced for real money.
I need some help in order to put together the parts of the big picture. So, I want to mine dogecoins. Using a web site I can connect to mining pool for dogecoins. So, these all mined coins should appear in my account there, right?
Then, using this tutorial it is said that using an "auto-sell" strategy with Cryptsy is nice. I can't get how both are connected - is Cryptsy used to transfer what you have produced to BTC? And where is the part when the coins are transferred to money?

Welcome to the Bitcoin SE, these kind of questions are a bit broad and not useful to anyone as the info can become outdated fast. Not to mention this is a popular google search item.

The basic idea is to find somebody else who is willing to pay money to obtain dogecoin. This is difficult to do by yourself, so there is the idea of an "exchange" where people who are interested in buying and selling can find each other.
You would create an account on an exchange, send your freshly mined dogecoin to your exchange account, and then put them up for sale at some price. Hopefully, another person who wants to buy dogecoin will meet your price. When the sale happens you would get some amount of dollars in your exchange account. Note that in order to sell your dogecoin, there must be another buyer who is willing to buy them. If nobody is willing to buy, you can't convert them to cash.
Finally, after a successful sale, you arrange with the exchange to withdraw your money into your bank account.

Thanks, are not there any website which are regularly buying your coins on transfer them to BTC?

Sure, there is a gigantic list of services at https://en.bitcoin.it/wiki/Trade


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If a wallet has multiple addresses, is the money in the wallet or in the address?
In the standard bitcoin client (Bitcoin-Qt), they tell me the total money in the wallet. However, should I be able to see how much money is in each address?
Does bitcoin money belong to an address or on a wallet?

How is this not a duplicate?

@PeterMortensen: A duplicate of what?  If you know of another question that this one duplicates, please use the "flag" button on this question to indicate that, and it can be closed with a pointer to the other question.

The bitcoins you received with an address are always associated with that address. The wallet is merely summing up the balances of individual addresses contained in the wallet. You can move addresses between wallets by exporting the private key from one wallet and importing them in another and the bitcoins will show up in the second wallet as well.

and the default client hide that from me. We can't even move money from one address to another in the same wallet.

I prefer to think of a wallet more like a keychain. There's a set of keys which unlock your coins


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Is there a service that let's me "send" bitcoins via email and doesn't require any account creation/login?
I'm familiar with the Coinbase and Blockchain.info approaches to this, but both these require registration/login (correct me if I'm wrong). I heard about something called Coinapult, but on visiting their website I don't see much about sending coins, and it says "not available in your country", and I'm in the U.S. I'm pretty sure I saw something for Dogecoin that does this, but not bitcoin.
Wouldn't there be some demand for a simple service that:

Lets you visit it on desktop/mobile web
Has no login or account needed to send or receive coins
Lets you specify a timeout and return to address if the recipient doesn't retrieve the coins in time
Generates and displays a recipient bitcoin address, QR, hyperlink for you to copy/paste, scan or click so that your bitcoin wallet gets the address or payment request.
Saves the private keys for the generated addresses in their own system, but with the idea that recipients of coins will be prompted to transfer funds to their own wallet.
Sends an email to the recipient with a hyperlink to gain access to a web form that lets them transfer the coins to any bitcoin address they choose.
Does not charge fees (maybe ad supported or maybe offers opportunity to download a wallet application) or maybe charges a very minimal transaction fee.

Anyway, does this exist for Bitcoin yet? Or what features above are missing or should get changed?

This is technically possible and can be easily implemented, but I see two problems, which may be stopping people from creating such a service:

Trust: how can the service ensure its clients that it will not
steal their money?
Security: email is not secure, a man in the middle can access the
email message on its way before the recipient, and steal the money.

If there is a solution to these two problems, there will be demand and implementations of such service.

Right, the "Trust" issue is valid, but perhaps initially it could be limited to sending small amounts of bitcoins, so maybe <$200 USD at a time, until trust is established. As for the security, well most people have all their password resets going to email anyway. This includes bank accounts, etc. So while not perfect, it should still work. Ideally the email is sent using ssl to the receivers email system.

Blockonomics email service does most of what you describe and doesn't require any login. Its distributed trust model ensures that you don't have to trust it with your private keys


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Any way to create a multisig address from Bitcoin addresses (instead of public keys)?
Any way to create a multisig address from Bitcoin addresses (instead of public keys)?
If not, why not? What would the problem be?
EDITED - Thanks for the answers. This is for an application that generates multisig transactions with escrow for external users. Of course anyone who controls an address can find the public key, but that's probably beyond many casual users (or too much of an hassle).

No. OP_CHECKMULTISIG only supports multiple pubkey not pubkeyhash (addresses).

So? OP_CHECKSIG only supports pubkeys, too.

This is possible, but there isn't really any code to do it automatically.
Instead of creating a scriptPubKey like
<pubkey 1> <pubkey 2> <pubkey 3> 2 OP_CHECKSIG

you'd make one like
OP_DUP OP_HASH160 <pubkeyhash 1> OP_EQUALVERIFY OP_ROT
OP_DUP OP_HASH160 <pubkeyhash 2> OP_EQUALVERIFY OP_ROT
OP_DUP OP_HASH160 <pubkeyhash 3> OP_EQUALVERIFY OP_ROT 2 OP_CHECKSIG

Also, the code of the receiver would need to change, in order to recognize the output as spendable.
It's probably much easier to get their public keys. If they've used their addresses on the network, you can look it up using https://blockchain.info/q/pubkeyaddr/<addr>
Example: https://blockchain.info/q/pubkeyaddr/1snowqQP5VmZgU47i5AWwz9fsgHQg94Fa
Or, you can use George Kimionis's method to decode addresses.

Thanks Nick, could you point me to George Kimionis's method to decode addresse?

That's just the answer below.

A problem is that many casual users don't know their public keys and are unable to find them, and others (e.g. Circle etc.) can't know them at all.

oops sorry I didn't see that

@NickODell Wow! Have you actually run this script? I'll give it a shot on testnet, bc as you know I love script stuff

@WizardOfOzzie I have not tested this. You should be able to spend it with a scripSig of 0 <sig> <sig> <key> <key <key>, though.


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How do I open an Armory .wallet file in the MultiBit Client?
Sorry, I'm incredibly new to this whole thing.  I started off using the Armory Client for my Bitcoin wallet then was suggested to try "MultiBit".  I've saved my .wallet file from Armory, however cannot open it in MultiBit.  Is this normal?  How does one use the same wallet?  Stick to one bitcoin client?  I also don't see the option to load a wallet on the original bitcoin client.  Is it just easier to setup a wallet with a service like blockchain?

Transactions that spend your balance from one wallet to an address in another wallet is one method to move your funds.

It is normal. Each Bitcoin client makes its own choices on how it stores its private keys and balance information. The main (Satoshi) client uses a BerkeleyDB database, BitcoinJ serializes its wallet object directly to file, and other clients do other things. While I'm not 100% certain how Armory or MultiBit store their wallets, chances are they've chosen different techniques which are not compatible. If you want to switch clients, I'd suggest generating a new wallet in your new client and using the old client to send all your coins there. If you have addresses that you'd like to keep from the old client, you'll need to find some way to export the private keys from the old and import them into the new via some standard they both support, like WIF (Wallet Import Format) private keys. Sadly, not every client will give you easy access to the private keys so it may not actually be possible - I'd refer to both clients' documentation for that answer.

Instead I only have .wallet.lmdb file is it possible to open it?


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How to read the transaction pages on blockchain.info?
I read the original Bitcoin paper and think I understand it but I'm having a hard time relating it to the transaction pages on blockchain.info.  For example, sometimes there are 2 outputs and neither of them is back to the sender (what the paper would call "change") which seems to violate the rules of splitting and combining described in the paper.
Is there a good guide on how to read these diagrams?

possible duplicate of Why does Bitcoin send the "change" to a different address?

Change for a transaction doesn't have to go back to the original address: part of it can be sent to the receiver, and the other part can go back to a new address. That way it's slightly harder to trace where the money went, as you don't know which part was the transfer and which part was the change.

The rules are pretty simple:

there are one or more inputs to a transaction
there are zero or more outputs to a transaction
any difference between the input and the output values is treated as a transaction fee and kept by whomever mined the block

In terms of a "change" address, it is simply another output.  It just happens to be one to an address to which you hold the private key.  As to if that address has already been used for something else, that's up to whatever software generated the transaction.


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How to build a web site on which clients can send and receive bitcoins without an account?
I've been asked to write a gambling website using bitcoins. The gambling part is easy but I found out about bitcoins only yesterday. I've been following the links and reading but I'm buried in technical jargon; like block chain, wallets, mining etc.
I just want to know the following things.

What does the website need to hold bitcoins?
What does the website need to request funds from player?
How to transfer funds from player to website?
What does the website need to give out funds to player?
How to transfer funds from website to player?

I'd like to know the answers to be as specific as possible, even code level.
Oh, a requirement is not need to open an account on my website or using any payment gateway.
Thank you all in advance.
Moe

Your question boils down to "please write me a guide how to set up a bitcoin driven webshop or even write it for me". This is a request that can not be easily answered in the stackexchange format. You might want to split it to several narrower questions or instead ask whether somebody knows of such a tutorial.

A payment gateway may have restrictions on the type of business category, and online gambling may be a category they don't support.
The process is pretty simply.
Supply a new address for each deposit.  When a payment arrives to that deposit address the customer account is credited.
A payment is considered final, generally, once it has six confirmations.  That may be a long time for a customer (an hour, or longer even) -- some sites use one, or three confirmations but then have withdrawal restrictions so that newly deposited funds are not withdrawn until the original deposited funds have six confirmations.
But this business deals with money. Any business that deals with money, whether dollars, euro, gold, or bitcoin, should not be operated without giving appropriate attention to the factors that require attention.  With Bitcoin being a non-reversable payments system, IT Security becomes among the most important areas of the business.
Learning how to construct a payment transaction (sendtoaddress using bitconid) or receiving a payment (poll bitcoind using listtransactions, or -walletnotify) should be your last concern at this point.  Figuring out how to manage a wallet, using a cold wallet and hot wallet, for example, and making sure you have backups, etc., are a higher priority.
This experience might be something you hire out for rather than solicit from a Q&A site.


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Where can I find bitcoin price charts?
I am trying to see some bitcoin charts but looks like all sites are down. Any help?

http://bitcoincharts.com/ works for me...

not for me at the moment..

We recently launched https://pizzacharts.com to provide gorgeous realtime crypto-charts.

http://bitcoincharts.com/charts/mtgoxUSD has historical charts.
These 3 all have 'live' charts:

http://btccharts.com/
http://mtgoxlive.com/
http://bitcoin.clarkmoody.com/

In my opinion, you should not use Mt. Gox as an indication of the price of Bitcoin.  The price on Mt. Gox is significantly higher than the other exchanges, because sellers must be compensated for the difficulty of getting their money off the site.  Instead, you might use BTC-e for pricing info. Here is the chart you ask for:
http://bitcoincharts.com/charts/btceUSD#rg1ztgSza1gWMAzm1g10zm2g25zvzcv


text:
How do the blue encrypted bitcoin paper wallets work?
Via https://www.bitaddress.org I saw you can get a paper wall but with encryption and a passphrase. What are the steps of using the wallet with the passphrase? It seems the address is on the left while the private key is on the right.  So I am guessing the private key is what's encrypted with the passphrase? How would you decrypt it with the passphrase?

When the time has come to spent your coins, whatever wallet software you use to scan the private QR code, will have to ask you for the passphrase.
Give it a try with one and any wallet app on your smartphone. You don't need to put any bitcoins on it.


text:
Difference between having bitcoin in my wallet or in a third party like an exchange or an e-wallet
Is there any difference or any problem or extra fees for having permanently (1 month, 6 months, etc..) my BTCs instead of having them in a local wallet like Bitcon-Qt or Multibit?

This really depends on the exchange website's policies. But in general money is a local wallet behaves just as what a wallet in real life would do: store money without any fees or interest. As long as you (and only you) own the wallet file (normally wallet.dat) you control whats being done with the money.
On the other hand, money stored on a website/exchange behaves very much like storing money in a bank. Fees or interest is based primarily off the website's policies. The main thing thats different is that they reserve the right to do things with your money. When you are sending money to a address they merely carry out your request for you.
Regarding long term storage a local wallet should retain all money you have as long as you own the wallet file and that no major changes to the bitcoin system itself occurs (extremely unlikely). For online exchanges, it depends on whether they choose to do anything with your money whilst you are not using it (e.g. remove it after x amount of inactivity). Needless to say if the website/exchange shuts down for whatever reason you probably can't get the money out again.
Given that a exchange/website employs a no-delete, no-cost policy it really just boils down to trust. Do you trust a third party with your money for whatever the benefits it may bring you or not?

Only the respective trade-offs of trusting another party with your money vs trusting yourself not to lose your data.
When you keep your money on an exchange website or online wallet service, you are not only trusting their good intentions, but also that they stay in business and are running a secure service. A significant number of exchanges and OWS have been compromised or put out of business.
When you keep your money on your own devices, you are trusting yourself not to be hacked, fooled into sending money to a wrong address, and to keep your data safe. The latter requires you to engage in a decent backup policy and to have a basic understanding what you are doing. There have been numerous cases of personal computers being compromised (google for example "AllInVain"), people losing their data to hardware failure without having a backup, or recently, someone just throwing his hard drive worth $7Mio in the garbage.

First let us know the difference between the private bitcoin wallet and Third Party wallets.
For bitcoin wallet the private key of the wallet is the key to your bitcoin wallet, so anyone who own/know can easily spend any money in that private key any time.
In private bitcoin wallets the private key is known to you only and you don't share with anyone else. It is more secure than a bank vault if executed properly. Here you are responsible for saving and securing the funds in your wallet and creating the public address for transactions etc. There are many offline wallet options like, desktop wallet client, a mobile offline wallet, any Paper bitcoin wallet or offline wallet hardware. There are no charges associated directly with
In Third party bitcoin wallets the private key of your account is held by the website, and most frequently they just show your bitcoin balance as reflected in their database and they use some cold-storage wallet to store the actual bitcoins of all the users at their site. Most of the time you can create only one or two public addresses, and all the payment to that address is associated your account. This online wallets generally charges on the basis of transaction value, the charges vary from 0.01% to 0.1% BTC per transaction. Most probably that don't charge you based on the time of duration you keep them in the wallet.
note: some Bitcoin wallet sites can delete your account if you don't access your account for some pre-defined time like 3-6 months. so read terms carefully.

I think another difference besides what have been said is,  when you put money in an e-wallet, the third party can accumulate a decent amount of money from all the users, and use it for short term investments. That's why you can use their service freely, or even get some interests. This is what I see in e-wallets like "WeChat pay" or "Alipay". However with bitcoin wallet, you are keeping your money in your own pocket all the time, and to use it you need to pay a so called "small" amount of fee.


text:
Transfer BTC from online wallet to paper wallet
I just wanted to post this here to make sure I am doing this exactly right.

I created an online wallet with block chain dot info (cant post links with my rep)
I am going to buy BTC's from bit bargain dot co dot uk and transfer the bitcoins to my online wallet created in step 1.
I used this tutorial (http://fieryspinningsword.com/2013/12/01/how-to-create-a-reasonably-secure-bitcoin-paper-wallet/) to create a 'reasonably secure' paper wallet (I even wrote down my keys instead of printing them off as noted in the 'extra security' bit at the end)
I shall then send all the BTC's from my Online wallet (step 1) to my paper wallet (step 3).

My question(s) are:

My paper wallet will still be secure? because I've only used the public key online — correct?
How can I confirm that the BTC's are in my paper wallet? I don't want to hold on to these suckers for 10 years, for them to be worth billions, to realise that I lost them in the ether when I come to sell/use them.

I used the tutorial to the letter, and took no further steps to create my paper wallet, if I missed something and it's not created properly, please let me know.

I'm going to be pedantic here.  There are three components to bitcoin addresses. 1: Private Key, 2: Public Key and 3: Receiving Address.  The receiving address is a hash of the public key.  A bitcoin address is the most secure when it has only ever had bitcoins sent to it as only the receiving address is publicly known.  To spend the bitcoins you create a transaction which contains the public key and a signed transaction - knowing the public key will make it easier (by orders of magnitude, but still huge) for an attacker to brute force.

My paper wallet will still be secure? because i've only used the public key online - correct?

Sure, if the wallet was created securely in the first place then sending to it's public key (address really) poses no threat to it.

How can I confirm that the BTC's are in my paper wallet?

You can use a block explorer like blockchain.info or blockexplorer.com to check the balance of your paper wallet address.
Might not hurt to do a trial run with a small amount first.


text:
Bitcoin-Qt frozen catching up/sync with Bitcoin in new wallet
I downloaded Bitcoin-Qt, got it running, had 15 weeks or so left to catch up (sync) when I purchased some bitcoins and had them sent to my new wallet.
Then to my horror, Bitcoin-Qt has frozen with four weeks to go. It has been running 48 hours without any change in changed blocks left. I have restarted my computer, rebooted the modem, all the simple things but no love.
What can I do to access this wallet? I'm new to all this. I only ever used my online wallet address before.

What version of Bitcoin-QT are you running? One of the newer versions significantly increased the synchronization speed.

If you still have the wallet.dat file from the bitcoin-qt installation at the time got the wallet address that you sent the money to you can use that with a new bitcoin-qt installation to try to make it work. If you don't have that wallet.dat file anymore the money is lost.
As for the problems downloading the blockchain, are you sure you have enough space? It's about 12 GB now. It sometimes take a very long time to download and may just look like it's sitting around for a while doing nothing, then pick up again a while later.

Yupp backed up wallet, before and after I encrypted it in my panic.... Was scared to uninstall and reinstall as I couldn't find anywhere to open a backed up wallet, as for space, I'd be really surprised to find I don't have 12 gig on my c drive, but will check that too when I get home, thanks heaps for help hey!!!

P.s. I figured 48 hours was long enough for it sitting around doing nothing before I called it frozen

@Ric you are probably right about 48 hours, though if you have space and waiting doesn't solve it I'm out of ideas. Hopefully someone else have some.

If all else fails you can export your private keys and import them into a different wallet, like Electrum.
To get your private keys out of bitcoin-qt, click Help, Debug Window, Console tab.
If your wallet is encrypted, you must unlock the wallet with this command:
   walletpassphrase "your wallet password" 60

To get the private key:
   dumpprivkey "addressYouOwn"


text:
Can a blockchain transaction history be updated by text messages using a mobile network?
Is it possible to update Bitcoin transactions over mobile networks using texts or voice data transmission?

No, at present this is not possible. The Bitcoin network runs only over the internet. (Of course, there are lots of mobile data networks in the world, and Bitcoin works just fine over those.)
One could imagine some kind of service to receive transactions by phone or text and relay them to the Bitcoin network (and perhaps vice versa), but I don't think such a service currently exists.  I'm not sure that very many people would find it useful.
What applications do you have in mind for such a feature?

for a widespread adoption of bitcoin in countries where sms/mms are already in use. The coins are stored on phone and messages can send and receive the transactions.


text:
Wallet is encrypted and currently locked. How can I get it decrypted (unlocked) - I have my password!
I have run into the problem of my wallet being encrypted and currently locked. I am using Bitcoin-Qt. I have my password to unlock it, but I can't find an area in the interface to unlock the wallet.
Where do I enter my password to unlock?

You will be asked for your password when you want to send coins.
Alternatively, you can unlock your wallet for a period of time using the walletpassphrase command in the console.

CLICK: Help
CLICK: Debug Window
CLICK: Console
Input the following command-line: walletpassphrase  9999999 true
 with the Password you created to Encrypt your Qt Wallet>.  Hit Enter after you type this phrase.
After you close the Console-Your the lock in the bottom bar will unlock (though you may have to look carefully to see the change.  If you hover your cursor over the lock you should see the phrase: "Qt Wallet is now ENCRYPTED AND UN-LOCKED- for block minting only."    The warning about your client being unable to mint should disappear also.


text:
Is it possible to run more than one client instance on a machine?
Is it possible to run more than one Bitcoin client at the same time on the same machine? I tried to set different working ports, but it seems not to be working.

You need both a different RPC port (-rpcport), a different P2P port (-port), and a different working directory (-datadir).  You will also need to use the daemon (bitcoind) for everything after the first instance, since only one GUI can be running at the same time.

Ok. I set all these parameters differently but again I am not able to run 2 bitcoin client together. Should I use the daemon bitcoind instead of bitcoin ? I am working on windows ...

Oh, yes. I believe only one GUI can be running at the same time as well.

Yes, using bitcoind after few tests it seem work!

I followed these steps and it worked. However, I can't get peers using a different P2P port, getpeerinfo is always empty. How can this be solved?

first you should run getpeerinfo using bitcoin-cli with datadir and addnode with the local ip and port


text:
How do I implement a Merkle Tree?
I`m slowly implementing some Bitcoin protocols, and I'm not sure how to properly understand the Merkle Tree from the Bitcoin wiki:
https://en.bitcoin.it/wiki/Protocol_specification#Merkle_Trees
I have strings a, b, c, I double-hash them and I get the three leaf nodes. But I'm not sure what to do with the higher nodes. Do I double hash the sum of the resulting bytes (treating them like big numbers), or do I concatenate (treating them like strings), or perhaps do I should something else?

In each iteration, you concatenate two subsequent hashes of the previous level, and double-sha256 them. If there is an odd number of hashes, concatenate the last element with itself.
This gives you a new list of hashes. Repeat, and stop when one hash remains. This is the merkle root.
Assume you have tx hashes Ha1,Ha2,Ha3,Ha4,Ha5,Ha6,Ha7

First iteration: Hb1=Hash(Ha1|Ha2), Hb2=Hash(Ha3|Ha4), Hb3=Hash(Ha5|Ha6), Hb4=Hash(Ha7|Ha7)
Second iteration: Hc1=Hash(Hb1|Hb2), Hc2=Hash(Hb3|Hb4)
Third iteration: Hd1=Hash(Hc1|Hc2) => Merkle root

You hash the hashes. See the bottom of https://en.bitcoin.it/wiki/Dump_format#CBlock for an image.

Bitcoin Core's merkle root calculation function can be found here. Here's the simplified version:
// Input: individual transaction hashes (a.k.a. leafs)
uint256 ComputeMerkleRoot(std::vector<uint256> hashes) {
    while (hashes.size() > 1) {
        // If there's an odd number of hashes
        if (hashes.size() & 1) {
            // Copy it to the end of the hashes array
            hashes.push_back(hashes.back());
        }
        // Compute double SHA256s of (hashes.size() / 2) blocks
        // Save the output to hashes
        SHA256D64(hashes[0].begin(), hashes[0].begin(), hashes.size() / 2);
        // Save the output to hashes
        hashes.resize(hashes.size() / 2);
    }
    // If there were no original hashes, return 0
    if (hashes.size() == 0) return uint256();
    return hashes[0];
}


text:
Where can I find a Bitcoin-related job?
Say I want to use a Bitcoin expertise I have and turn that into a career. Is there any website listing job offers related to Bitcoin that I could use? Alternatively, if I am someone looking for Bitcoin-savvy people to employ, where should I start looking?

related: This guy was looking for a Bitcoin consulting services.  Perhaps we should have a jobs section to handle this need.

You are describing, the new cottage industry -- that of The Bitcoin Specialist.
There are a lot of skills that can be combined to become self employed providing Bitcoin-related services.
There is profit that can be made when trading bitcoins in-person.  There are hundreds of individuals who are signed up with LocalBitcoins and offer this personal buying and/or selling service.  Adding a fee or offering an exchange rate in your favor from five to fifteen percent versus the market rate is not uncommon, though that is temporary as competition will bring the rates more in line with market prices over the long run.

http://www.LocalBitcoins.com

There is the need for IT security assistance.  It could be as simple as helping a person understand two-factor authentication and setting up Google Authenticator to secure access to the user's exchange account.
Individuals who don't know what an "air gap" is might be willing to pay to be shown how to create an offline paper wallet using a LiveOS on a system that has no network connectivity -- purposely disabled for security purposes.  Or set up an Armory offline wallet and demonstrate how it is used:

http://www.BitAddress.org
http://bitcoinarmory.com/index.php/using-offline-wallets-in-armory

More and more Bitcoin-related services, including #bitcoin-otc marketplace, MPEx, and FastCash4Bitcoins.com for example, require GPG. Setting that up for people (and showing how to back up the GPG private key) is a needed support service.
Online there are people who simply want to move their funds from their own wallet to an EWallet and can't be bothered with updating the software and/or waiting for the blockchain to finish downloading.   But they might be willing to attach their wallet.dat (if encrypted) or upload it (via https) to someone offering wallet transfer services.
There are people locally who might be interested in speculative trading who would pay for the education -- not just market-timing trading on the exchanges but perhaps investing on MPEX, or ICBit.se (futures) as well.
There may be individuals who would love to play BitLotto, bitZino and SatoshiDICE but don't know what "provably fair" means.  So being able to demonstrate why these can be considered "provably fair" and explain how they can be used is a service that gamblers might pay for.
Bitcoin is just one of the components in the tool chest.  Just as knowing Bitcoin very well opens some doors, knowing other privacy-enhancing technologies can be valuable as well.   Tor and to a lesser extent mesh networking are two other skills a Bitcoin technology consultant will want to have expertise in.
There may be people willing to transact on the dark net but they don't already have the technical ability to do so.  Having someone local who is familiar with the steps (e.g., install Tor, install GPG, coin mixing, etc.) and can perform assistance in getting set up, in-person, is a valued service.  [Though be careful, and don't offer this service unless you really know your stuff.]  Consider joining or starting a CryptoParty:

http://www.CryptoParty.org

Local escrow is another service.  A person might not trust an online escrow but if they already know who you are, in real life, they might be more willing to use you as escrow for a trade.
Somewhat related to escrow is to act as a buyer's agent.  For instance, someone is buying something from a seller in your town and wishes to ensure a good transaction.   So you accept the buyer's payment and then you meet the seller to inspect the goods before shipment. If the items are in working order you settle up (paying cash to the seller), and the shipment goes out.
Additionally, now that ASICs are just about to ship, a person can provide tech services to non-technical people.  The BFL equipment will still need a host, whether it is a Raspberry Pi or a desktop computer.  Unlike GPU and to a lesser extent FPGAs, the ASIC equipment does not require strong technical skills.  A miner can be set up in minutes, with only periodic maintenance.  Because there is not much heat produced nor any extraordinary connectivity requirements, ASIC mining is once again putting mining back in the range of capabilities of a typical slightly ambitious person.
Just look at all the ways bitcoins are used and there are unmet needs all over the place.

I'm pretty sure coinality (https://coinality.com) is what you're looking for. A board for jobs and freelance offers in the cryptocurrency space. Right now there are dozens of job offers online, mainly in the US though.
good luck & let us know if you actually find a job in the crypto space!


text:
Which exchanges still accept USD wire transfers? (Oct 2012)
Are there any exchanges left accepting USD wire transfers? I heard mention of sending to Dwolla and then transferring to Intersango, but only for U.S. citizens.

Dwolla is only for this in the U.S. and the type of bank transfer they do is ACH, which is specific to banks in the U.S.
As far as exchanges that accept wire transfers directly, there are many, including:

Mt. Gox (Japan)
BitStamp (EU)
BitFloor (U.S.)
BTC-E (Russia)
Bitcoins Direct (U.S.) (bulk sales, minimum $500)

Many various methods here:

http://en.bitcoin.it/wiki/Buying_bitcoins


text:
How can I hide my bitcoin transactions to protect anonymity?
I read many related questions about the pseudo-anonymity and bitcoin transaction tracking.
So if I understand correctly, bitcoins, or better, transactions can be tracked for their entire lifetime.
Example user case:

I buy bitcoins from Mt.Gox
I send some bitcoins here and there
Now I decide to send 50 BTC to a person (Bob) who did a job for me, in the hope that nobody finds out about my deal.
Bob changes the 50 BTC recently received in dollars through Mt.Gox

Now, if I'm right, it is possible to track back the transaction to me, since all transactions are public. And so everyone knows that part of the money changed by Mt.Gox was used to pay Bob and that he changed them back to dollars.
This is true as long as my address and Bob's address is also known.
Is there some way to break the transaction history of the bitcoins from Mt.Gox?
I mean, for example, would it be possible for Bob to transfer the 50 BTC to Mt.Gox from an unknown address that was never used, so it can't be associated to my address? Or is it possible to send bitcoins only from the reveicer address?
Situation when using the same address to receive and send bitcoins:

[Mt.Gox] ==> [Me] == [Bob] ==> [Mt.Gox]
Situation with new generated addresses:

1. [Mt.Gox] ==> [Me]
2. [Me] == [Bob]
3. [Bob] ==> [Mt.Gox]
In short, how to hide where bitcoins came from?
I read there is a way to generate new addresses and send through them. Is that true?
Thanks :)

Bitcoin is not anonymous. Don't expect it to be.

Right. Privacy and anonymity are seperate issues. You can make a transaction very private so that Bob will know who sent the Bitcoin, but very few others would be able to trace it to you. Law enforcement should have tools to trace transactions, but even for them it should not be easy.

anonymous !=  pseudo-anonymity

It is possible to trace Bitcoins all the way back to the blocks they were mined, although it might be a hard task. Similarly, one can also trace them back to any withdrawal from MtGox, as long as we know which transaction to look for. No matter how many times you send them from one address to another, it is still possible to trace them back to that transaction, especially if you send the full amount each time.
If you want to make it way harder for someone to trace the transaction, you'd need some service that would take your Bitcoins, send them to some address that is used in many transactions and send them back to some other address you own. There have been many services like this started, but I don't know of any that had the traffic volume necessary to obscure anything. This option assumes that the service would not keep track of the finished transactions, thus not being able to reveal information about you.
You can also try "laundering" your Bitcoins by paying someone to send you Bitcoins from another address. Similarly, you could pay someone to mine a fresh block of Bitcoins for you. Similar as above, it only works if the person would not keep information about you.
Lastly, you could just order some physical Bitcoins. Trading them is completely offline, so nobody can trace who you gave the coins to. I'm not sure though if Casascius keeps any order data, which could be later linked to the person that redeemed the coins at some point in the future.

also you could use a litecoin exchange. then whoever is tracking your transactions will need to use two different blockchains and the exchange's logs (if they keep them). do this with a few different exchanges and the chances of anyone tracking you aproach zero

Laundering services are a big gamble - you never know if they'll really give you a different coin or just run away with your money. Casascius were a great option, but its minting has stopped as of Xmas/2013 due to Uncle Sam sending letters to its owner. Already minted coins will now become highly valued collectibles.

All you need to do is send your bitcoins to MtGox and withdraw them to a new address.  MtGox processes so many bitcoin deposits and withdrawals that you've very unlikely to get the same coins back, and so nobody (other than MtGox and anyone with access to their database) would be able to tie your deposit together with your withdrawal.  Alternatively, make 2 MtGox accounts, deposit into one, use a 'redeemable code' to transfer the coins to the other account, and withdraw from there.  Then even MtGox can't be sure the coins didn't change hands.

Every person owns several addresses, and for most addresses keeps the association with himself private. In your scenario coins move from address A of Mtgox, to your address B, to Bob's address C, back to Mtgox address D. The only people who know that address B belongs to you and address C belongs to Bob - and hence deduce that you paid Bob - are you, Bob and Mtgox.
Any large eWallet can double as a mixing service, and there are also dedicated mixing services. You can bounce your funds through several such services, and then all of them will have to release your info in order to associate you with an address.
To avoid some weaknesses of using a centralized mixing service, it is also possible to perform peer-to-peer oblivious mixing transactions, as discussed here.

Don't send money from your own wallet to Bob.
Send it directly from MtGox.
That way, it is not associated with your wallet (just with MtGox, whose wallet is shared by half of the Bitcoin world).
All these online wallet services are essentially anonymizing mixers.
On might argue that then MtGox knows that you sent money to Bob, but a) they don't care, b) if they care, they could track it in the chain anyway, as you point out above, c) they don't know that the address you sent to belongs to Bob.
One thing you must make clear to Bob, however, is that under no circumstances is he supposed to send anything back to the address where his coins came from (because then MtGox has no idea what to do with them). But this is a general principle of Bitcoin that a sending address cannot just be used as a receiving address as well. If there are any refunds or the like, you need to give Bob another address for that (preferably a completely new one).

There are great amount of gambling's sites. Just go with TOR(onion routing) to poker room, and wash your money in one of rooms. Your fantasy is your friend.

Download Torr web browser took kit
get onto internet via Torr
Via torr, open a new hushmail account, lets call this hush1, use random name info.
use that new email to open a new wallet at blockchain.info
Log back onto hushmail and create a second hushmail account, call this hush 2, use random info to create this account as well.
Use that to create a second blockchain.info wallet
using the wallets at blockchain info is a problem due to email verification of attempts to log in,  if you have time use a Yubikey as second verification. If you don't have time then just use the email verification of each log in attempt.
Empty your wallet from mt gox into Hush1,
pay the fee to mix and send to Hush 2
Pay the fee again, and mix and send to bob.

Draw this on a peice of paper to see it and understand the flow.
There would be little or no way to tell for sure anything except that you got rid of your bitcoins.  There would be no way to tell who ended up with them, or even tell that you own the account called hush2.
bob is in the clear, if he created his wallet anonymously like a paper wallet from bitaddress.org then he is totally clean.  You however have to understand that someone (mt gox) knows you had some bitcoins and that you sent them off into the world.
You could also use the hush2 account to open an account at BTC-E and trade your bitcoins almost totally anonymously.  ( I have checked this out, and it seems possible, they don't have much in the way of verification of identity, but they will log your IP address ( torr takes care of this) and they will know your contact info like email, (Hushmail takes care of this)
The Yubikey is a good tool to use for second verification,  I have one on order to try this set up, but have not done it yet.
YOU ALSO MUST PRINT OUT A PAPER COPY OF YOUR WALLET FROM YOUR ACCOUNTS, JUST AS A BACKUP, BUT NOW YOU HAVE TO HIDE THAT PAPER, AND NOT SOMEWHERE OBVIOUS LIKE YOUR SAFE.
You can keep it pretty safe,  if you are willing to try.
There doesn't need to be a bob,  you can just clean your coins to yourself this way. you end up with clean coins in an anonymous account.
Mt Gox is the weak link,  they are the ones in this senario that need your info.
(torr hides who you are, and your IP)
(hushmail gains you access to open accounts via anonymous email)
(remember not to pay for your hushmail accounts, use  the free service so they can't track who you are through you payment for a premium service)
by using Torr to create anonymous emial addresses, then using those emails to create anonymous wallets, then using the mix features at blockchain.info, you have pretty well covered your tracks.
is it alot of work?? yes.
is it actually better than pretending you threw away 7 million dollars worth of bitcoins on a hard drive at the landfill???  certainly.
what % of "stolen" bitcoins are not really stolen???  sounds to me like you can avoid some taxes pretty easy by claiming you lost your coins,  then someday just take a vacation somewhere sunny and show up and claim your wallet and never come back.    7 million would be a pretty long vacation.

Note sure if this helps anyone, but I can imagine a scenario, similar to @larry1265's, wherein you encrypt your connection to the web, use a proxy (relatively easy to set up) and then create emails addresses from a provider not associated with you. Then, use this process to download and set up your wallet, eg, Armory, and follow the best practices. Wouldn't this secure a fair bit of anonymity?

Okay, A wants to send to B, but wants to hide the chain.  Enter a matching service.  The matching service makes a record of A wanting to send to B and waits until C wants to send to D.  Then it tells A to send to D and C to send to B and charges a commission.  Then everyone is happy and there is no link from A to B.
However in practice this may be a little dicey.  Suppose A and B are in the Green mafia and C and D are in the Blue mafia.  So now the police are investigating a link between the Green and the Blue mafias.

The main problem with Bitcoin anonymity is that every transaction is publicly logged by design. Anyone can view the flow of Bitcoins from address to address in the blockchain. This data alone cannot be used to identify you because the addresses are just random numbers, but if any of the addresses in a transaction's future or past history can be backtraced to a real identity, it may be possible to find out who owns all the other addresses. Such identity information could be derived from network analysis, surveillance, or a quick google search for the bitcoin address.
here is the list of mixing servises, use them to avoid compromising of privacy and security. Mixing services provide to periodically exchange your bitcoins for different ones which cannot be associated with the original owner.
https://en.bitcoin.it/wiki/Mixing_service

One of the approaches to preserves confidentiality is ECDHM that is an Elliptic Curve Diffie Hellman Merkle Bitcoin address scheme to enhance privacy. ECDHM addresses can be shared publicly, and are used by senders and receivers to secretly derive traditional Bitcoin addresses that passive blockchain observers cannot predict. The result is that ECDHM addresses can be "reused" without the loss of privacy that usually occurs from traditional Bitcoin address reuse. More detailed information is founf here: http://wiki.openbitcoinprivacyproject.org/topics:ecdhm-address


text:
How is address recognized between wallets
Lets assume I create a wallet in Jaxx and Bittrex for ETH token which in turn creates public & private key pair. I am able to transfer coins between different wallets.
How is the address generated by Jaxx recognized by Bittrex wallet ? Is it because the underlying process of (PGP) generation of public key is same ?
How different is this process from PGP ?

Addresses are a standard encoding of data used by Bitcoin and other altcoins. When you enter an address into a wallet, it will decode it in the specific way that all wallets know to decode an address.

How different is this process from PGP ?

PGP has nothing to do with Bitcoin (or cryptocurrencies) at all whatsoever.

Will all the wallets use the same decoding schema for a coin like for example ETH. How would a wallet know. Are there any chances of collision ?

Presumably yes, they use the same encoding. A wallet would not know whether the same encoding is used; they just assume that it is and decode things as such. If it is not the same encoding, then the decoding will likely fail.


text:
i sent bitcoin from my coinbase account to my bittrex account but i used the Bitcoin cash address on accident
I have sent bitcoin from my coinbase account to my bittrex account but i have used my bitcoin cash address from bittrex on accident, Where did my money go and is there a way i could access it thru chain block and if so how can i do that? Please help me out with this i'm fairly new to this and don't know what to do, How can i get my money back?
Thank you in advance

You can try contacting Coinbase and/or Bittrex, however when you open your bitcoin cash wallet on Bittrex it clearly says, "Depositing tokens to this address other than BCH may result in your funds being lost", so there's no guarantee.