Key Negotiation
Niels Ferguson, Bruce Schneier, Tadayoshi Kohno · 2015
This chapter explains how to tackle the key negotiation protocol. It presents a sequence of protocols, each of which adds a bit more functionality. There are different methods for designing key negotiation protocol, some with supporting proofs of security and some without. Modifying a protocol and still keeping it compatible with older versions is rather complicated. We have to implement several versions of the protocol, with a system to decide which version to use. Successful protocols live almost forever. So it is even more important to design protocols to be future-proof. The chapter introduces an authentication convention as protocols break because they neglect to authenticate certain data fields. In the authors' protocols, every time a party sends an authentication, the authentication data consists of all the data exchanged so far. The authenticator will also cover the identities of the communicants.