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A Bitcoin Laundry or Mixing Service is a service that accepts BTC payments, and returns the same BTC amount, only from coins that are unassociated to the original BTC. It is a privacy service that works well if it has massive usage.

What are some good mixing services? Is there any data on how well they actually anonymize (e.g. what size are their "stashes" or user base (bigger stash = bigger anonymity)?

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A large part of the confusion surrounding mixers is simply a mixture of poor grammar and terminology. As was shown to me in this question there is no distinct recognizable item corresponding to a "bitcoin" the way there is corresponding to, say, a dollar. It might be better to say that mixers disguise the transaction chain leading to your account by passing through one or more intermediaries. There is no such thing as a "dirty" coin, just data that can be tracked back to "dirty" sources –  David Perry Oct 11 '11 at 14:26
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It doesn't disguise by adding layers like a Tor node does. Rather, you give it "dirty coins", it gives you "clean coins" - coins that someone else gave it, that have absolutely nothing to do with your coins (they might be accidentally dirty from some other source, but they are not dirty from anything you did with them). –  ripper234 Oct 11 '11 at 14:42
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But you could do the same thing without the mixer. Just transfer the 'dirty coins' to Mt. Gox and then withdraw. Nobody would know it's you without compromising the recipient in either case. (In one case, it's Mt. Gox. In the other case, it's the mixer. I'd say Mt. Gox is more trustworthy than the mixer anyway.) –  David Schwartz Oct 11 '11 at 15:11
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@DavidSchwartz - Mt Gox could be looked at as a 'mixer' of sorts but they don't provide any "service level agreement". Looking at my transactions some rapid round trips through Mt. Gox are very obfuscated others however appear to be put into infrequently used accounts and it may be possible w/ sufficient block chain analysis to identify/track the funds. A superior mixing service would be one that mixes large amounts of transactions through multiple iterations and in/out addresses involving random periods of time. Of course as you point out trust is a major issue. –  DeathAndTaxes Oct 12 '11 at 2:05
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@DeathAndTaxes: True, but such tracking wouldn't be useful. At best, an attacker could tell that someone transferred funds to Mt. Gox and someone withdrew funds from Mt. Gox, getting the same coins. There's no way they could tell they're the same person. If you want to be crazy, deposit the Bitcoins into an anonymous Mt. Gox account and get a Mt. Gox code. Deposit that into your account two weeks later. Nobody but Mt. Gox could track that. –  David Schwartz May 7 '12 at 9:32

7 Answers 7

up vote 10 down vote accepted

The only one I'm currently aware of is "Bitcoin Laundry" operated by Mike Gogulski. They charge a 4.555% commission rate and do little more than accept a payment then re-send a payment. There is also (according to the Wiki) that the service is only lightly used and might not be adequate to provide any real anonymity. You might be better sending then withdrawing coins at Mt Gox with a decent delay between transactions - the sheer volume of Mt Gox's transactions as well as the size of their wallet would make them much more effective and there's nothing I'm aware of to stop you from creating an account with a throwaway email address and accessing Mt Gox through TOR/I2P/etc.

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Looking at the Bitcoin Laundry it does seem to be poorly implemented. A good laundry should have sufficient transaction volume possibly even paying other entities to provide entropy by including transactions they don't need "washed". It also at least according to the website doesn't do any transaction splitting (i.e. 500 BTC in via one transactions and 500 BTC over a period of 18 transactions spanning 3 days with balances between 12.02 and 278.45) which would appear to provide nothing more than "feel good" obfuscation. –  DeathAndTaxes Oct 12 '11 at 2:08
    
The current commission rate is 1.9%. –  Daniël W. Crompton Oct 5 '13 at 22:35

Blockchain.info has recently started up a dedicated mixing service.

Send Anonymously with Blockchain

As they were offering bonus payouts at the start I sent money via the service and it was quickly forwarded to the correct account.

To confirm how they mix the coins and the amount of taint remaining you can check the source code on github.

Source code

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What do you mean by "bonus payouts"? –  Pacerier Jun 2 at 8:49
    
They were offering 1% return on coins for anyone who used it. So they pay you for fresh coins to give them coins to mix with. It was a short term offer. –  MaxSan Aug 16 at 22:54

CoinJoin is being tested and is working https://bitcointalk.org/index.php?topic=282086.20

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would you please elaborate a bit on the contents of the link? –  Murch Oct 29 '13 at 11:02
    
@Murch Dark Wallet has been showed to the world and it uses the CoinJoin implementation that Pablo and Amir made, mentioned in that link. –  rdymac Nov 4 '13 at 18:23

The blockchain-based betting services could essentially be used as a mixing service, where the makeup of a wallet is significantly different after several passes through the wagering service.

It still leaves a direct trace but the set of coins held initially is mostly gone ne and the composition of the wallet after is mostly coins that weren't there before.

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But since it's not designed to do so, I wouldn't be so sure everything would work smoothly. –  Lohoris May 8 '12 at 9:33

I came across Bitcoinfog at http://www.bitcoinfog.com/. They run a hidden service in TOR at http://fogcore5n3ov3tui.onion

They have been down since mid August 2012 and are not back up as of Nov 2012. I first thought they cut and ran with peoples bit coins. Which is quite a risk for sites like this. It's happened to me before as well when I was "testing the waters" by running the coins through a tumbler site.

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The second paragraph was not added by me, and represents another user's experience. –  Crispy Oct 24 '13 at 16:36

http://BitcoinBath.com looks pretty promising as a bitcoin mixer. They aren't fully out of beta testing yet but keep an eye out, they are sure to the lead bitcoin tumbler in technology soon.

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How do you know that they look promising, if they aren't out of beta yet? Please tell us whether you are affiliated with BitcoinBath. –  Murch Oct 17 '13 at 13:56

I've been using blockchain.info and MixBit (mixbity3bxwsqmnn.onion). I really like the fact that MixBit works in Tor and doesn't need javascript nor account.

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