Paper 2020/1565

Achieving privacy and accountability in traceable digital currency

Amira Barki and Aline Gouget

Abstract

Several Central Bank Digital Currency (CBDC) projects are considering the development of a digital currency that is managed on a permissioned blockchain, i.e. only authorized entities are involved in transactions verification. In this paper, we explore the best possible balance between privacy and accountability in such a traceable digital currency. Indeed, in case of suspicion of fraud or money laundering activity, it is important to enable the retrieval of the identity of a payer or a payee involved in a specific transaction. Based on a preliminary analysis of achievable anonymity properties in a transferable, divisible and traceable digital currency systems, we first present a digital currency framework along with the corresponding security and privacy model. Then, we propose a pairing-free traceable digital currency system that reconciles user's privacy protection and accountability. Our system is proven secure in the random oracle model.