Practically-exploitable Cryptographic Vulnerabilities in Matrix

Martin R. Albrecht; Sofía Celi; Benjamin Dowling; Daniel Jones

Paper 2023/485

Practically-exploitable Cryptographic Vulnerabilities in Matrix

Martin R. Albrecht, King's College London

Sofía Celi

, Brave Software

Benjamin Dowling

, University of Sheffield

Daniel Jones

, Royal Holloway University of London

Abstract

We report several practically-exploitable cryptographic vulnerabilities in the Matrix standard for federated real-time communication and its flagship client and prototype implementation, Element. These, together, invalidate the confidentiality and authentication guarantees claimed by Matrix against a malicious server. This is despite Matrix’ cryptographic routines being constructed from well-known and -studied cryptographic building blocks. The vulnerabilities we exploit differ in their nature (insecure by design, protocol confusion, lack of domain separation, implementation bugs) and are distributed broadly across the different subprotocols and libraries that make up the cryptographic core of Matrix and Element. Together, these vulnerabilities highlight the need for a systematic and formal analysis of the cryptography in the Matrix standard.

Metadata

Available format(s): PDF
Category: Attacks and cryptanalysis
Publication info: Published elsewhere. 44th IEEE Symposium on Security and Privacy, S&P 2023
Keywords: secure messaging end-to-end encryption attacks protocols real-world cryptography secure group messaging
Contact author(s): martin albrecht @ kcl ac uk
cherenkov @ riseup net
b dowling @ sheffield ac uk
dan jones @ rhul ac uk
History: 2023-04-05: approved; 2023-04-04: received; See all versions
Short URL: https://ia.cr/2023/485
License: CC BY

BibTeX

@misc{cryptoeprint:2023/485,
      author = {Martin R. Albrecht and Sofía Celi and Benjamin Dowling and Daniel Jones},
      title = {Practically-exploitable Cryptographic Vulnerabilities in Matrix},
      howpublished = {Cryptology ePrint Archive, Paper 2023/485},
      year = {2023},
      note = {\url{https://eprint.iacr.org/2023/485}},
      url = {https://eprint.iacr.org/2023/485}
}