IPLS: Privacy-preserving storage for your WhatsApp contacts

What this post added

Introduced Identity Proof Linked Storage (IPLS), a novel system for WhatsApp that allows users to store contact names in an encrypted way. IPLS leverages client-generated encryption keys, authentication based on primary device identity, and integrates with WhatsApp's existing Auditable Key Directory (AKD) and Hardware Security Modules (HSM). The system uses AKD to map phone numbers to identity keys and partners with Cloudflare as a witness for AKD updates. Contact names are encrypted with a device-generated symmetric key and stored in HSM-based Key Vaults, enabling secure restoration on new devices.