In order to further incentivize work in this space there is now a multisignature escrow bounty fund:
3M8XGFBKwkf7miBzpkU3x2DoWwAVrD1mhk (yes, Bitcoin addresses can also start with a 3)This is a two-of-three multisignature escrow with myself, Theymos, and Pieter Wuille as signers. To release any coin sent to this address at least two of these people must sign the transaction.
The bounty fund will pay out as funds are available according to the signers best judgment for completed work proposed in this thread that furthers the goal of making improved transaction privacy a practical reality for Bitcoin users.
Please feel free to contribute to the above address to support work on this infrastructure.
I would like to make a claim on this fund for work done on Compact Confidential Transactions (subject to the ongoing peer review).
https://bt.irlbtc.com/view/1085436.msg11597427CoinJoin should 'just work' in this scheme, and has a similar interface to gmaxwell's Confidential Transactions for keeping participant's balances hidden from other participants.
Participants generate some random inputs, and same number of random outputs, to themselves with a zero sum, and ensure that they do not introduce any fuzz over/underflow, so the fee is fixed.
An alternative approach, is to let participants share only their fee delta, guaranteeing that everyone makes the same fee adjustment, in which case the number of outputs can also differ to the number of inputs for each participant.
If anyone puts in too much or too little, their sum, and the whole transaction sum, won't come out as zero and the transaction will be invalid.
