AbstractWe construct a language extension for process calculi for modelling the exchange of cryptographically composed data. More specifically, we devise a succinct syntax for terms and patterns that captures the intention behind perfect cryptography. The proposed language extension is independent of the choice of process calculus and is applicable to any calculus that supports exchange of data. Initially we restrict the model to symmetric cryptography, but we also show how it can be extended with support for asymmetric encryption and digital signatures.