Welcome to the resource topic for 2025/2007
Title:
k-Anonymous Group Signatures: Addressing Strict Content Moderation in End-to-End Secure Messaging Platforms
Authors: Shalini Banerjee, Andrey Bozhko, Andy Rupp
Abstract:We review k-anonymity in authentication schemes, group signatures and ring signatures. While existing constructions achieve unlinkability, they typically necessitate maintaining state or relying on computationally expensive tracing algorithms. We propose a stateless variant that is efficiently traceable, albeit necessarily fully linkable. To the best of our knowledge, our variant, which we call k-Anonymous Group Signatures (k-AGS), is the first scheme to combine both statelessness and efficient traceability.
Building upon our k-AGS framework, we design k-Anonymous Set Pre-Constrained Group Signatures (k-ASPCGS) which is a threshold extension of the Set Pre-Constrained Group Signatures (SPCGS) introduced by Bartusek et al. (EUROCRYPT 2023).
We show that our notions arise naturally in the context of lawful surveillance, particularly for end-to-end secure messaging platforms, where controlled traceability is essential. Beyond this setting, they may also help mitigate the impact of strict moderation policies in large-scale distributed asynchronous platforms (e.g. Facebook, whistleblowing portals) as well as in spam control, where false positives remain a persistent challenge.
ePrint: https://eprint.iacr.org/2025/2007
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