The Post-Quantum Signal Protocol : Secure Chat in a Quantum World

The Signal Protocol provides end-to-end encryption, forward secrecy, backward secrecy, authentication and deniability for chat applications like WhatsApp. The Signal Protocol does this by using the ECDH Curve25519 key exchanges and SHA-512 key derivation. However, the ECDH key exchange is not quantum-safe. A post-quantum Signal Protocol requires a substitute for the ECDH key exchanges. Therefore, we look at post-quantum cryptography, which is secure against a quantum computer. In this thesis we analyse the Signal Protocol and explain our research. We compared 11 different post-quantum algorithms: SIDH and 10 different key encapsulation mechanism, which are in the NIST post-quantum standardisation process: BigQuake, BIKE, Frodo, Crystal-Kyber, Leda, Lima, New Hope, Saber, SIKE and Titanium. We conclude that it is feasible to have different post-quantum Signal Protocols considering the state of 2018 for an average user.