Riposte: An Anonymous Messaging System Handling Millions of Users

TL;DR

Riposte is a scalable anonymous messaging system that protects against traffic analysis and denial-of-service, supporting millions of users with novel privacy techniques.

Contribution

It introduces a system that combines privacy, scalability, and security for anonymous broadcast messaging using innovative techniques from private information retrieval.

Findings

Supports nearly 2.9 million users in 32 hours

Protects against traffic analysis and malicious clients

Scales to large user bases with secure multi-party computation

Abstract

This paper presents Riposte, a new system for anonymous broadcast messaging. Riposte is the first such system, to our knowledge, that simultaneously protects against traffic-analysis attacks, prevents anonymous denial-of-service by malicious clients, and scales to million-user anonymity sets. To achieve these properties, Riposte makes novel use of techniques used in systems for private information retrieval and secure multi-party computation. For latency-tolerant workloads with many more readers than writers (e.g. Twitter, Wikileaks), we demonstrate that a three-server Riposte cluster can build an anonymity set of 2,895,216 users in 32 hours.