Bitcoin Forum

Trust free mixers have the problem that you need to trust the mixer to not reveal the participants, or conversely, trust the participants not to DoS attack the mix by failing to sign the transaction.

However, enter Distributed Hash Tables! Er, I mean fidelity bonds.

Each participant buys a chaum token with their bond, and then submits a txout they want to see in the next round of mixing. They also commit to a hash of the txins they promise to sign before the round deadline.

Now they reconnect to the mixer under a new identity (think tor circuits) and sign the transaction inputs. If everyone does sign the txins required before the end of the round, great! The tx is complete and can be sent out.

If anyone doesn't, not so great, however each participant can get their chaum totkens reissued back by revealing what txins they initially promised to sign. The person(s) who didn't meet the deadline lose their tokens.

Of course, it could be done as straight up fees as well, but with the bonds you could re-use the right to talk to the mixer over and over again - each txout can be associated with a new pubkey that gets the right to another chaum token.