The Role of Trust in Information Integrity Protocols

Paradoxically, one of the most important { and at the same time, probably one of the least understood { functions performed by information integrity protocols is to transfer trust from where it exists to where it is needed. Initially in any protocol, there are at least two types of trust: trust that designated participants, or groups of participants, will faithfully execute their assigned function in the protocol and trust in the integrity of the transfer mechanism(s) integral to the protocol. Consequently, almost all protocols enforce a set of restrictions as to who may exercise them { either spelled out explicitly or left implicit in the protocol speci cation. In addition there may be unanticipated or even unacceptable groupings of participants who can also exercise the protocol as a result of actions taken by some of the participants re ecting trusts that exist among them. Formal methods are developed to analyze trust as a fundamental dimension in protocol analysis and proof.