The Modelling and Analysis of Security Protocols: the CSP Approach

6.2. Modelling the intruder: the perfect spy

Recall from Section 2.3 that we need to model a malicious intruder, bent on acquiring information that should be maintained secret among the agents, or on sowing confusion among them so as to undermine their trust in one another.

The intruder has two major tasks: information gathering, by overhearing or destructively capturing messages; and misinformation, by faking messages from data in his possession. The only restriction we usually impose is that he should not be able to manipulate cryptographically protected message components without access to the appropriate keys. These two tasks have to be connected by an information repository, storing data items that have either been learnt directly, or are ...