Enhancing the security of WhatsApp calls

This post details the technical implementation and security benefits of two new optional features in WhatsApp calls: 'Silence Unknown Callers' and 'Protect IP Address in Calls'. 'Silence Unknown Callers' uses a specialized protocol enforced by WhatsApp servers to deliver stripped-down, silenced call notifications, protecting recipients from complex call setup processing and potential zero-click attacks. This is achieved through a novel privacy token system that allows clients to locally decide trusted users and distribute tokens, enabling servers to validate call initiation without learning the exact caller-recipient relationship. 'Protect IP Address in Calls' relays calls through WhatsApp servers to hide user IP addresses from other parties, preventing the deduction of geographical location. This is achieved by shifting from peer-to-peer connections to a relay model, ensuring end-to-end encryption remains intact.