Formal methods for assuring security of protocols

Establishing the security of a system is an intricate problem with subtle nuances: it requires a careful examination of the underlying assumptions, abstractions, and possible actions. Consequently, assuring that a system behaves securely is virtually impossible without the use of rigorous analytical techniques. In this article, we focus on a single cryptographic protocol (Needham-Schroeder) and show several different formal methods can be used to identify its various vulnerabilities. These vulnerabilities include susceptibility to freshness attacks and impersonations.