## Paper: Proof Techniques for Cryptographic Processes (at LICS 1999)

**Michele Boreale Rocco De Nicola Rosario Pugliese**

### Abstract

Contextual equivalences for cryptographic process calculi can be used to reason about correctness of protocols, but their definition suffers from quantification over all possible contexts.Here, we focus on two such equivalences, may-testing and barbed equivalence, and investigate tractable proof methods for them. To this aim, we develop an `environment-sensitive' labelled transition system, where transitions are constrained by the knowledge the environment has of names and keys.On top of the new transition system, a trace equivalence and a co-inductive weak bisimulation equivalence are defined, both of which avoid quantification over contexts. Our main results are soundness of trace semantics and of weak bisimulation with respect to may-testing and barbed equivalence, respectively.This leads to more direct proof methods for equivalence checking. The use of such methods is illustrated via a few examples concerning implementation of secure channels by means of encrypted public channels. We also consider a variant of the labelled transition system that gives completeness, but is less handy to use.

### BibTeX

@InProceedings{BorealeDeNicolaPugl-ProofTechniquesforC, author = {Michele Boreale and Rocco De Nicola and Rosario Pugliese}, title = {Proof Techniques for Cryptographic Processes}, booktitle = {Proceedings of the Fourteenth Annual IEEE Symposium on Logic in Computer Science (LICS 1999)}, year = {1999}, month = {July}, pages = {157--166}, location = {Trento, Italy}, publisher = {IEEE Computer Society Press} }