Paper 2021/629

Bitcoin Privacy - A Survey on Mixing Techniques

Simin Ghesmati and Walid Fdhila and Edgar Weippl

Abstract

Blockchain is a disruptive technology that promises a multitude of benefits such as transparency, traceability, and immutability. However, this unique bundle of key characteristics rapidly proved to be a double-edged sword that can put user privacy at risk. Unlike traditional systems, Bitcoin transactions are publicly and permanently recorded, and anyone can access the full history of the records. Despite using pseudonymous identities, an adversary can undermine the financial privacy of users and reveal their actual identities using advanced heuristics and techniques to identify eventual links between transactions, senders, receivers, and consumed services (e.g., online purchases). In this regard, a multitude of approaches has been proposed in an attempt to overcome financial transparency and enhance user anonymity. These techniques range from using mixing services to off-chain transactions and address different privacy issues. In this survey, we particularly focus on comparing and evaluating mixing techniques in the Bitcoin blockchain, present their limitations, and highlight the new challenges.