Publication

On Ends-to-Ends Encryption: Asynchronous Group Messaging with Strong Security Guarantees

ACM Conference on Computer and Communications Security (CCS)


Abstract

In the past few years secure messaging has become mainstream, with over a billion active users of end-to-end encryption protocols such as Signal. The Signal Protocol provides a strong property called post-compromise security to its users. However, it turns out that many of its implementations provide, without notification, a weaker property for group messaging: an adversary who compromises a single group member can read and inject messages indefinitely.

We show for the first time that post-compromise security can be achieved in realistic, asynchronous group messaging systems. We present a design called Asynchronous Ratcheting Trees (ART), which uses tree-based Diffie-Hellman key exchange to allow a group of users to derive a shared symmetric key even if no two are ever online at the same time. ART scales to groups containing thousands of members, while still providing provable security guarantees. It has seen significant interest from industry, and forms the basis for two draft IETF RFCs and a chartered working group. Our results show that strong security guarantees for group messaging are practically achievable in a modern setting.

Related Publications

All Publications

USENIX Security - February 22, 2021

SocialHEISTing: Understanding Stolen Facebook Accounts

Jeremiah Onaolapo, Nektarios Leontiadis, Despoina Magka, Gianluca Stringhini

CODE - November 20, 2020

Privacy-Preserving Randomized Controlled Trials: A Protocol for Industry Scale Deployment (Extended Abstract)

Mahnush Movahedi, Benjamin M. Case, Andrew Knox, Li Li, Yiming Paul Li, Sanjay Saravanan, Shubho Sengupta, Erik Taubeneck

USENIX Security - November 11, 2020

Deep Entity Classification: Abusive Account Detection for Online Social Networks

Teng Xu, Gerard Goossen, Huseyin Kerem Cevahir, Sara Khodeir, Yingyezhe Jin, Frank Li, Shawn Shan, Sagar Patel, David Freeman, Paul Pearce

ACM IMC - October 28, 2020

Towards A User-Level Understanding of IPv6 Behavior

Frank Li, David Freeman

To help personalize content, tailor and measure ads, and provide a safer experience, we use cookies. By clicking or navigating the site, you agree to allow our collection of information on and off Facebook through cookies. Learn more, including about available controls: Cookies Policy