Depends on the system you're keying. BEST has their own IIRC (bestaccess.com i think)
Also
www.dlaco.com has versions that I think is more generic. I'm not really much of one for using software for that, though I've never really spent much time with master keying beyond personal use and the Matt blaze paper. The intricacies of enormous systems may elude me although mathematically, I think I see how they work. (large installations)
