I don't understand why don't they just use PGP, or something like that. There is no patent on it?

IDEA is patented in Europe. It takes a lot of time to test out and "break in" new encryption algorithms. If you invent one, surely the first thing you would want to do is to patent it, right? Well, that is exactly what everyone's been doing so far. Few, if any, actually let their stuff go to the public domain. Kudos to Bruce S for Blowfish ... Ern