Compact Multi-Party Confidential Transactions

“Confidential Transactions”, integrated transactions of commitments, signatures, and zero-knowledge range proofs, are favored for their ability to hide transaction amounts. In the real world, multi-party fund transfers are highly desirable for personal and business security. Unfortunately, existing unproven Multi-Party Confidential Transactions are linear in the (exact) number of co-owners; hence they are not compact, very scalable, nor private (leak number of users and their public information). In this study, we provide provably secure private, compact Multi-Party Confidential Transactions, in both the “unanimous” N-out-of-N and “threshold” T-out-of-N settings. Unlike other schemes, our multi-party transactions have the size of single-owner transactions and hide the number of participants. To the best of our knowledge, ours is the first proven secure multi-party and threshold confidential transaction protocol.