I was reading the Serenity PoC2. The part quoted below grabbed my attention.
Does it imply full anonymity for Ethereum transactions should I decide to use the ring signature mixer?
Ring signature mixer – part of the test.py script now includes creating an instance of a ring signature verification contract which is designed as a mixer: five users send their public keys in alongside a deposit of 0.1 ETH, and then withdraw the 0.1 ETH specifying the address with a linkable ring signature, simultaneously guaranteeing that (i) everyone who deposited 0.1 ETH will be able to withdraw 0.1 ETH exactly once, and (ii) it’s impossible to tell which withdrawal corresponds to which deposit. This is implemented in a way that is compliant with the gas checker, providing the key advantage that the transaction withdrawing the 0.1 ETH does not need to be sent from an additional account that pays gas (something which a ring signature implementation on top of the current ethereum would need to do, and which causes a potential privacy leak at the time that you transfer the ETH to that account to pay for the gas); instead, the withdrawal transaction can simply be sent in by itself, and the gas checker algorithm can verify that the signature is correct and that the mixer will pay the miner a fee if the withdrawal transaction gets included into a block.
Best Answer
Nope. Nothing in blockchain is fully anonymous. Just very difficult to track down. Almost to the point of not worth trying to unless you did something really bad and there's proof it came from your address. And even then. Linking address to identity is difficult in and of itself.