Paper 2019/925

Fully Auditable Privacy-preserving Cryptocurrency Against Malicious Auditors

Wulu Li, Yongcan Wang, Lei Chen, Xin Lai, Xiao Zhang, and Jiajun Xin

Abstract

Privacy protection techniques have been thoroughly studied in the current blockchain research field with the famous representatives such as Monero and Zerocash, which have realized fully anonymous and confidential transactions. However, lack of audit can lead to abuse of privacy, and can help bad guys to conduct illegal activities, such as money laundering, transfer of illegal assets, illegal transactions, etc. Therefore, it is crucial to study the privacy-preserving cryptocurrency with full auditability. In this paper, under the framework similar to Monero, we propose FAPC, a fully auditable privacy-preserving cryptocurrency with security against malicious auditors. FAPC mainly consists of three schemes: a traceable and linkable ring signature scheme (TLRS), a traceable range proof (TRP), and a tracing scheme for long-term address (TSLA). In FAPC, the identities of UTXOs, transaction amounts and the corresponding long-term addresses can be traced by the auditor with maintaining anonymous and confidential to others. The constructions of TLRS and TRP are simple and modular, which only use standard ring signature as component, without any additional one-time signatures or zero-knowledge proofs. The TSLA is constructed by usage of standard ring signature and ElGamal encryption to realize traceability of long-term addresses in transactions. Moreover, all the schemes are secure against malicious auditors to realize a closer approach towards decentralization. We also give the security proofs and implementations of our schemes, as well as the performance results.

Note: We give the first construction of the fully auditable privacy-preserving cryptocurrency against malicious auditors by usage of traceable and linkable ring signatures (TLRS), traceable range proof (TRP) and tracing scheme for long-term address (TSLA). If you have comments or suggestions, please contact us by e-Mail.