On the Automation of Gny Logic

The cryptographic protocol analysis logic of Gong, Needham and Yahalom (GNY) ooers signiicant advantages over its predecessor, the Burrows, Abadi and Needham (BAN) logic. Manual analysis of protocols using the GNY logic, however, is cumbersome , as the logic has a large set of inference rules. This paper proposes a modiied GNY logic, and describes the implementation of a protocol analysis tool based on that logic. The modiications ensure that no useful inferences are lost, and allow the logical statements derivable from a given protocol to be deduced in a nite number of steps. The tool ooers a facility to automatically generate proofs of protocol goals. It has proved useful in mechanically verifying the need for several inference rules which are all absent from the original GNY logic.