It is well known that users on open blockchains are tracked by an industry
providing services to governments, law enforcement, secret services, and alike.
While most blockchains do not protect their users’ privacy and allow external
observers to link transactions and addresses, a growing research interest
attempts to design add-on privacy solutions to help users regain their privacy
on non-private blockchains.
In this work, we propose to our knowledge the first censorship resilient
mixer, which can reward its users in a privacy-preserving manner for
participating in the system. Increasing the anonymity set size, and diversity
of users, is, as we believe, an important endeavor to raise a mixer’s
contributed privacy in practice. The paid-out rewards can take the form of
governance tokens to decentralize the voting on system parameters, similar to
how popular “DeFi farming” protocols operate. Moreover, by leveraging existing
“Defi” lending platforms, AMR is the first mixer design that allows
participating clients to earn financial interests on their deposited funds.
Our system AMR is autonomous as it does not rely on any external server or
third party. The evaluation of our AMR implementation shows that the system
supports today on Ethereum anonymity set sizes beyond thousands of users, and a
capacity of over $66,000$ deposits per day, at constant system costs. We
provide a formal specification of our zksnark-based AMR system, a privacy and
security analysis, implementation, and evaluation with both the MiMC and
Poseidon hash functions.