I knew both Jon Millen and Sid Clark well and generally kept up with their work.I heard more than one presentation of Millen's Interrogator at national 'IEEE Security and Privacy Symposium's.  http://www.ieee-security.org/TC/sp-people-history.htmlJon's Interrogator was for a number of years perhaps the most well-known tool used to crack security protocols.Inversely, the protocol was (partially) -formally- verified if the Interrogator couldn't crack it.Sid had written a Prolog interpreter while at UNH and the Interrogator was written in Prolog.It seems that one may now have to pay to get a copy of a paper on the Interrogator.J.K. Millen, S.C. Clark, S.B. Freedman, "The Interrogator: Protocol Secuity Analysis," IEEE Transactions on Software Engineering, pp. 274-288, February, 1987