As end-to-end encrypted messaging services become widely adopted, law enforcement agencies have increasingly expressed concern that such services interfere with their ability to maintain public safety. Indeed, there is a direct tension between preserving user privacy and enabling content moderation on these platforms. Recent research has begun to address this tension, proposing systems that purport to strike a balance between the privacy of “honest” users and traceability of “malicious” users. Unfortunately, these systems suffer from a lack of protection against malicious or coerced service providers. In this work, we address the privacy vs. content moderation question through the lens of pre-constrained cryptography [Ananth et al., ITCS 2022]. We introduce the notion of set pre-constrained (SPC ) group signatures that guarantees security against malicious key generators. SPC group signatures offer the ability to trace users in messaging systems who originate pre-defined illegal content (such as child sexual abuse material), while providing security against malicious service providers. We construct concretely efficient protocols for SPC group signatures, and demonstrate the real-world feasibility of our approach via an implementation. The starting point for our solution is the recently introduced Apple PSI system, which we significantly modify to improve security and expand functionality.
CITATION STYLE
Bartusek, J., Garg, S., Jain, A., & Policharla, G. V. (2023). End-to-End Secure Messaging with Traceability Only for Illegal Content. In Lecture Notes in Computer Science (including subseries Lecture Notes in Artificial Intelligence and Lecture Notes in Bioinformatics) (Vol. 14008 LNCS, pp. 35–66). Springer Science and Business Media Deutschland GmbH. https://doi.org/10.1007/978-3-031-30589-4_2
Mendeley helps you to discover research relevant for your work.