Currently no one knows (or is saying they know) how to
encrypt 7800
carts.
Actually, I seem to recall that a guy in rec.games.video.classic has
figured it out, but there hasn't been any practical application of it
yet. But I haven't read r.g.v.c in a LONG time, so things may have
changed...
I wish I could remember his name... he was one of the big cheese techie
types in the newsgroup that was always hacking up weird stuff, so I don't
doubt that he did it.