End-to-end encryption (E2EE) for messaging has become an industry standard and is widely implemented in many applications. However, applying E2EE to audio calls, particularly group calls, remains a complex challenge. Unlike text messages, audio calls involve capturing audio streams from each participant, which must be combined into a single, coherent audio stream that all participants can hear. This is known as audio mixing. In a non-E2EE system, the audio is mixed by a central server, and the result is sent to each participant. In contrast, in an E2EE system, each audio stream must be encrypted locally and sent to every participant in the group call. This method presents major challenges with respect to network overhead, audio synchronization and limitation on applying audio enhancement techniques.
In this talk, we present a new approach using Fully Homomorphic Encryption (FHE), which enables end-to-end encryption for group voice calls. Concretely, we introduce blind audio mixing and an FHE-compatible compression technique.
