"Williamson, Keith" wrote:

I would like to receive any pointers to work that has been done applying category theory to computer security.

there is a paper by nancy durgin, john mitchell and me, describing a process calculus and logic for reasoning about security protocols. it should be on my web page http://www.kestrel.edu/home/people/pavlovic/ . the process calculus induces an action category, which is very briefly described in the paper. the point is that the categorical structure captures the static (design-time) composition of protocols. in a way, the category thus displays some sort of denotations of protocols. the analysis then proceeds by attaching axiomatic semantics to the morphisms. -- dusko