in(Secure) messaging apps — How side-channel attacks can compromise privacy in WhatsApp, Telegram, and Signal

Messaging applications have been around since the inception of the internet. But recently, due to the increased awareness around mass surveillance in some countries, more users are installing end-to-end encrypted apps dubbed “secure instant messaging applications.” These apps claim to encrypt users’ messages and keep their content secure from any third parties.

However, after a deep dive into three of these secure messaging apps — Telegram, WhatsApp and Signal — we discovered that these services may not fulfill the promises they are meant to keep by putting users’ confidential information at risk.

This is a serious problem, considering users download these apps in the hopes that their photos and messages will stay completely protected from third parties. These apps, which have countless users, cannot assume that their users are security educated and understand the risk of enabling certain settings on their device. As such, they have an obligation to explain the risks to users, and when possible, adopt safer defaults in their settings. In this post, we will show how an attacker could compromise these applications by performing side-channel attacks that target the operating system these apps delegated their security to. This post will dive into the methods in which these apps handle users’ data. It will not include deep technical analysis of these companies’ security.

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