Cryptographic Protocol Explication and End-Point Projection

Jay McCarthy and Shriram Krishnamurthi

European Symposium on Research in Computer Security (ESORICS) 2008

Cryptographic protocols are useful for engineering trust in transactions. There are several languages for describing these protocols, but these tend to capture the communications from the perspective of an individual role. In contrast, traditional protocol descriptions as found in a state of nature tend to employ a whole-protocol description, resulting in an impedance mismatch.

In this paper we present two results to address this gap between human descriptions and deployable specifications. The first is an end-point projection technique that consumes an explicit whole-protocol description and generates specifications that capture the behavior of each participant role. In practice, however, many whole-protocol descriptions contain idiomatic forms of implicit specification. We therefore present our second result, a transformation that identifies and eliminates these implicit patterns, thereby preparing protocols for end-point projection.

Concretely, our tools consume protocols written in our whole-protocol language, WPPL, and generate role descriptions in the cryptographic protocol programming language, CPPL. We have formalized and established properties of the transformations using the Coq proof assistant. We have validated our transformations by applying them successfully to most of the protocols in the SPORE repository.

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