Lockmix: a secure and privacy-preserving mix service for Bitcoin anonymity

Bitcoin has attracted considerable attention from governments, banks, as well as researchers. However, Bitcoin is not a completely anonymous system. All transaction information in the Bitcoin system is published on the network and can be used to reveal the identity of the user by transaction correlation analysis. In this paper, a secure and privacy-preserving mix service for Bitcoin anonymity, Lockmix, is proposed. Lockmix introduces mix servers to provide a mix service for the user by using blind signature and multi-signature schemes to prevent attackers from linking the input address with the output address. Lockmix provides anonymity, scalability, accountability, Bitcoin compatibility and anti-theft. Lockmix has been implemented on a Bitcoin test network, and experiments show that our solution is efficient.