Paper 2024/1407 Original: eprint.iacr.org/2024/1407 ↗

Encrypted MultiChannel Communication (EMC2): Johnny Should Use Secret Sharing

Abstract

Nowadays, the problem of point-to-point encryption is solved by the wide adaptation of protocols like TLS. However, challenges persist for End-to-End Encryption (E2EE). Current E2EE solutions, such as PGP and secure messengers like Signal, suffer from issues like 1) low usability, 2) small user base, 3) dependence on central service providers, and 4) susceptibility to backdoors. Concerns over legally mandated backdoors are rising as the US and EU are proposing new surveillance regulations requiring chat monitoring. We present a new E2EE solution called Encrypted MultiChannel Communication, based on n-out-of-n secret sharing. EMC2 splits messages into multiple secret shares and sends them through independent channels. We show that multiple independent channels exist between users and EMC2 provides E2EE with no single point of trust, no setup, and is understandable by the general public. Our solution complements existing tools and aims to strengthen the argument against legally enforced backdoors by demonstrating their ineffectiveness.