Reducibility Among Protocols

Recently considerable attention has been given to designing provably secure cryptographic protocols. Three basic problems that have been studied are: exchange of secrets, contract signing, and certified mail. Several protocols have been proposed for these problems. These solutions are very diverse in nature: they are secure under different assumptions, have different probabilities of cheating, and require different number of message exchanges. Consequently, there is a need to investigate the underlying relationships between these problems. In this paper, we study reducibilities among these problems, i.e. how a protocol for one problem can be transformed into a protocol for another problem, preserving (roughly) the operating conditions.