关键词: 区块链, 混币, 交易隐私, 一次性环签名, 混合加密

Abstract: Abstract:In order to solve the problems of the current blockchain coin mixing system that is difficult to resist the repeated transfer attack of users, the leakage of information by the mixing center, and the attack of forged transfer while protecting the privacy of user transactions, a blockchain coin mixing scheme based on one-time ring signature was proposed. First, funds were deposited into the mixing center and a request to join a ring group was made by the user. Then, after being verified by the mixing center, a one-time ring signature was used by the user to apply for a transfer. Finally, the signature and transfer instructions were verified by the mixing center, and the transfer was executed. The nature of the one-time ring signature makes it impossible for the mixing center to confirm whether the signature is from the user ring group, but not from which user, and the one-time ring signature can only be verified once, so while protecting the user's privacy, the user cannot send the transfer instruction repeatedly, and the mixing center cannot forge the transfer instruction. On the other hand, the communication between the user and the mixing center uses hybrid encryption technology, which effectively prevents third-party attackers from breaching the sending/verification of signatures and obtaining transaction privacy. The experimental results show that the average response time of the scheme increases linearly with the increase of the number of users, and the response time increases by about 10ms for each additional 10 users, and there will be no sharp decline or even paralysis of the system performance caused by the increase in the number of users, which can support multiple users in the mixing network to complete the transfer efficiently and smoothly under the premise of protecting the privacy of transactions. In the case of the same number of users, the response time is improved by about 60ms compared with Coinjoin, and about 80ms compared with Coinshuffle, which is not much different from Blindcoin and Blindmixing, but has the advantages of simple implementation and high security. Therefore, this scheme has practical and application value in protecting the privacy and property security of blockchain users.

Key words: Blockchain, coin mixing, transaction privacy, one-time ring signature, hybrid encryption