Protocol Variants and Electronic Identification

It is important to be able to evaluate information security systems involving humans. We propose an approach in which we consider the system as a cryptographic protocol, and users are modeled as ordinary players. To model the fact that users make mistakes that affect security, we introduce protocol variants that model mistakes or combinations of mistakes. By analysing the base protocol and its variants, and at the same time considering how likely each variant is, we get a reasonable estimate of the real security of the system. Our work takes the form of a case study of four Norwegian federated identity systems, as well as two proposals for improved systems. The four systems span a good mix of various types of federated identity systems.