Cloudflare helps verify the security of end-to-end encrypted messages by auditing key transparency for WhatsApp

Cloudflare has developed and deployed an Auditor service on Cloudflare Workers to verify WhatsApp's Key Transparency audit proofs. This service guarantees the global uniqueness and validity of epochs (versions of WhatsApp's Auditable Key Directory). The uniqueness is achieved using Durable Objects for timestamping, and validity is ensured by a Rust-based containerized service that performs compute-intensive tree validation using the `verify_consecutive_append_only` method. Epoch data is temporarily stored in R2 for validation. This contributes to the broader capability of security posture management by providing an independent audit mechanism for critical cryptographic infrastructure.