10 bitcoins (nearly 4000 USD) is offered for help with breaks, cryptanalysis, security proofs, analysis or improvements relating to the CCT protocol which aims at making the amounts of bitcoin transactions confidential with a dedicated efficient  zero-knowledge method. The timing is tight: the price expires on 20 of January.

Additional cash prizes, challenges and bounties on similar questions in applied financial cryptography and crypto research will be announced soon at this blog.