On Multiple Statements from Trusted Sources


Raphael Yahalom
Affiliation: Hebrew University and MIT
Abstract: The design of a distributed cryptographic protocol reflects assumptions about the characteristics of the environment in which the protocol will execute, as well as the participating entities' perspectives regarding these characteristics. One important such type of perspective is that of trust. It reflects how an entity perceives the characteristics of another entity and, in particular, the actions it expects that the other will perform under different circumstances.

Trust can be classified into different primitive trust classes. Each trust aspect is associated with different characteristics of the trusted entity. Consequently, trust of one entity in another in one aspect does not necessarily imply trust of the first entity in the second in any other aspect.

In protocols in realistic wide-area-network settings, an entity may receive multiple statements from multiple sources. Each source may be associated with different trust characteristics. The receipient needs to draw consistent conclusions given these multiple statements. A reasoning framework that guarantees valid deductions in the face of multiple statements is presented. We demonstrate aspects of that framework in the context of example protocols.

For more information, contact yahalom@pluto.mscc.huji.ac.il.