Echomix: a Strong Anonymity System with Messaging

TL;DR

Echomix is a practical, robust mix network framework that offers strong metadata privacy and resistance to advanced attacks, with low latency and bandwidth overhead, suitable for secure messaging.

Contribution

The paper introduces improvements to mix network designs, a new cryptographic group messaging protocol, and hybrid post-quantum encryption, enhancing security and privacy.

Findings

Resists traffic analysis and active attacks

Supports reliable group messaging with strong privacy guarantees

Employs hybrid post-quantum encryption for future-proof security

Abstract

Echomix is a practical mix network framework and a suite of associated protocols providing strong metadata privacy against realistic modern adversaries. It is distinguished from other anonymity systems by a resistance to traffic analysis by global adversaries, compromised contacts and network infrastructure, quantum decryption algorithms, and statistical and confirmation attacks typical for multi-client messaging setting. It is implemented as Katzenpost, a robust software project, and used in multiple deployed systems, and features relatively low latency and bandwidth overhead. The contributions of this paper are: (1) Improvements on leading mix network designs, supported by rigorous analysis. These include solutions to crucial vulnerabilities to traffic analysis, malicious servers and active attacks. (2) A cryptographic group messaging protocol with strong metadata protection guarantees and reliability. (3) Hybrid post-quantum nested packet encryption.