Deploying key transparency at WhatsApp

What this post added

Introduced a new cryptographic security feature for WhatsApp based on key transparency, enabling automatic verification of secure connections. Developed and open-sourced the Auditable Key Directory (AKD) library in Rust, which forms the foundation for this feature. The AKD maintains an append-only directory of public keys mapped to user accounts and generates publicly auditable change logs, strengthening end-to-end encryption guarantees by allowing clients to automatically validate encryption keys and providing a transparent, verifiable record of key changes. This system complements existing manual security code verification by offering an automated, scalable solution, particularly beneficial for large groups or frequent key changes.