Who Let the $\mathcal {DOGS}$ Out: Anonymous but Auditable Communications Using Group Signature Schemes with Distributed Opening

Abstract

Over the past two decades, group signature schemes have been developed and used to enable authenticated and anonymous peer-to-peer communications. Initial protocols rely on two main authorities, Issuer and Opener, which are given substantial capabilities compared to (regular) participants, such as the ability to arbitrarily identify users. Building efficient, fast, and short group signature schemes has been the focus of a large number of research contributions. However, only a few dealt with the major privacy-preservation challenge of group signatures; this consists in providing user anonymity and action traceability while not necessarily relying on a central and fully trusted authority. In this paper, we present $\mathcal {DOGS}$, a privacy-preserving Blockchain-supported group signature scheme with a distributed Opening functionality. In $\mathcal {DOGS}$, participants no longer depend on the Opener entity to identify the signer of a potentially fraudulent message; they instead collaborate and perform this auditing process themselves. We provide a high-level description of the $\mathcal {DOGS}$ scheme and show that it provides both user anonymity and action traceability. Additionally, we prove how $\mathcal {DOGS}$ is secure against message forgery and anonymity attacks.