International Association
for Cryptologic Research

In 2023, WhatsApp announced its deployment of key transparency, a feature which aims to decrease the trust placed on a centralized server when distributing public keys used for end-to-end encrypted messaging. Similar deployments have been announced for Apple iMessage and ProtonMail.This talk discusses the integration between WhatsApp and Cloudflare to audit the key transparency data structure within a live environment.

Earlier this year, WhatsApp announced their plans to launch key transparency for all WhatsApp users. Key transparency solutions help strengthen the guarantee that end-to-end encryption provides to private, personal messaging applications in a transparent manner available to all. In this presentation, we will cover how key transparency works, what the improved end user experience is for those wishing to verify their contacts' public keys, and various deployment challenges and considerations we encountered when building our key transparency system. We also have released an open-source library called Auditable Key Directory (AKD) which we use in our deployment, and can potentially serve as a reference point for others that wish to deploy key transparency in the future.

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