Pellaeon Lin

This report’s key findings are translated into Chinese, it has an accompanying FAQ, and the FAQ is translated into Simplified and Traditional Chinese. We performed the first public analysis of the security and privacy properties of MMTLS, the main network protocol used by WeChat, an app with over one billion monthly active users. We found that MMTLS is a modified version of TLS 1.3, with many of the modifications that WeChat developers made to the cryptography introducing weaknesses.

What does this research contribute to what we already know about WeChat? WeChat is an app with many features. Previously, we studied the privacy issues surrounding its Mini Programs, as well as its surveillance and censorship of text and image messages. In this research, we focus on WeChat’s network encryption protocol and its security.

This report is part one of a two-part series on a privacy and security analysis of the WeChat ecosystem. We’ve created an FAQ to accompany this report. Key findings This work performs the first analysis of WeChat’s tracking ecosystem. Using reverse engineering methods to intercept WeChat’s network requests, we identified exactly what types of data the WeChat app is sending to its servers, and when.