Asynchronous BFT Asset Transfer: Quasi-Anonymous, Light, and Consensus-Free
Timothé Albouy, Emmanuelle Anceaume, Davide Frey, Mathieu Gestin, Arthur Rauch, Michel Raynal, François Taïani
TL;DR
The paper tackles private, efficient asset transfer in asynchronous Byzantine environments by introducing QAAT, a modular system that combines Agreement Proofs (AP), commitments, universal accumulators, and zero-knowledge proofs to achieve quasi-anonymity, lightness, and consensus-freedom. AP provides a transferable proof of agreement that enables deterministic progress without relying on full consensus, while ZK proofs and accumulators preserve confidentiality and compact verification. The resulting QAAT algorithm maintains per-process storage of $O(\\boldsymbol{\lambda}+(|T|/n)\\log n + n)$ and overall communication of $O(\\boldsymbol{\lambda} n)$, and it supports receiver anonymity and transfer confidentiality through cryptographic primitives. The work also discusses practical enhancements, such as transfer batching and key rotation, and outlines future directions toward fuller anonymity and permissionless scalability.
Abstract
This paper introduces a new asynchronous Byzantine-tolerant asset transfer system (cryptocurrency) with three noteworthy properties: quasi-anonymity, lightness, and consensus-freedom. Quasi-anonymity means no information is leaked regarding the receivers and amounts of the asset transfers. Lightness means that the underlying cryptographic schemes are \textit{succinct} (\textit{i.e.}, they produce short-sized and quickly verifiable proofs) and each process only stores its own transfers while keeping communication cost as low as possible. Consensus-freedom means the system does not rely on a total order of asset transfers. The proposed algorithm is the first asset transfer system that simultaneously fulfills all these properties in the presence of asynchrony and Byzantine processes. To obtain them, the paper adopts a modular approach combining a new distributed object called ``agreement proof'' and well-known techniques such as commitments, universal accumulators, and zero-knowledge proofs.