A methodology is presented for using a general-purpose state enumeration tool, Murφ, to analyze cryptographic and security-related protocols. We illustrate the feasibility of the approach by analyzing the Needham-Schroeder (1978) protocol, finding a known bug in a few seconds of computation time, and analyzing variants of Kerberos and the faulty TMN protocol used in another comparative study. The efficiency of Murφ also allows us to examine multiple terms of relatively short protocols, giving us the ability to detect replay attacks, or errors resulting from confusion between independent execution of a protocol by independent parties