Someone needs to fire up Tor/I2P/etc and make a "Coin Wash" site.
Someone sends in an arbitrary amount of BTC along with multiple new addresses. The BTC that go in are broken into randomly-sized portions and sent to the new addresses at random intervals, interleaved with other transactions (minus a fee of course). If multiple coin washers existed they could also send coins to each other with instructions to forward. If such nodes also ran their own private testnet of sorts (zero fee) and sent mountains of arbitrary transactions with the right format it could be quite difficult even for even the ISP to sort the real transactions from the fake (see: chaffing and winnowing).
I think the above should be sufficient to beat analysis-based attacks, using Tor or I2P beefs up protection against analysis a bit more and I trust that the security already bundled in the bitcoin client should cover the rest.
Have I missed anything?
never used it but think this is something like that
http://bitcoinlaundry.com/can listen to more about it here
http://agoristradio.com/?p=407The problem with something as simple as bitcoinlaundry is that simple network analysis undoes your anonymity. If Alice wants to send Bob 3.14 BTC without it being traceable, bitcoinlaundry says "hand it to Charlie and have Charlie hand it to Bob" which, in the context of bitcoin, is a good start because at least it keeps your address off the books and all someone could conceivably discover is that you sent coins to Charlie, right?
Problem #1: if Dave has the ability to watch what Charlie sends and receives, he can pretty easily see that Alice sent in 3.14 BTC and soon after Charlie sent that exact amount to Bob - unless your transaction is an amount that a huge volume of others will be sending (1 BTC even perhaps) it is easily identified. Charlie could also be scrutinized by watching the timing of several known transactions and then observing the money in/out timing of unknown transactions.
Problem #2: Since Charlie operates on the open internet under his real name his equipment (and wallet) could be seized by the authorities quite easily. It's very difficult to do this sort of thing properly without keeping at least temporary records of where money came from and where it is destined.
Problem #3: Even if you solve problem 1 and 2, chances are that Charlie isn't performing enough transactions each day to properly disguise who sent what to whom. Even if he is, such data is not made available and neither Alice nor Bob have any way of knowing whether their transaction will be securely hidden among the transactions of others. Charlie could easily generate many fake transactions to hide the valid ones, but I don't know how similar testnet (or namecoin or any blockchain branch really) traffic looks to valid BTC traffic when sniffed offhand, I may be barking up the wrong tree on this one.
Much like running an exchange the security and thought process that must go into a coin washer are NOT trivial. Unlike an exchange, the first time one of these gets hacked it'll probably be by the government and people will probably go to jail as a result, so if anyone takes this and runs with it - DO IT RIGHT.