It's encrypted using SHA-255; in theory half as secure as SHA-256 but in practice they spend ten times long trying to work out why nothing is working properly.
Being semiserious I do wonder how hardcore you could do encryption in 8-bit processors. Like, how hard would it be to keep "nation state" level cracking out of your private messages for a week or so?
You could probably generate elliptic curve keys pretty effectively even with an Apple II, at least enough that you'd have to throw a couple of dozen Israels worth of intelligence agency at it to pop it.
