Provable security of internet protocols

Secure communications over the Internet are typically established by first running an authenticated key exchange protocol, which computes a secret key between two users, which is then utilised in an encryption protocol. In this work we examine novel security properties of the most prominent communications protocols, including the Transport Layer Security and Secure Shell protocols. We introduce new security frameworks for analysing security properties of protocols involving negotiation, multiple ciphersuites, long-term key reuse, and time synchronisation. Our results have increased confidence in the security of real-world protocols, and our analyses of next-generation protocols have informed their development by standardisation bodies.