I have seen no indication anywhere that it is PGP. Just that it's strong. I
don't know what algorithm they're using.
> the key on the computer is a public key, which has not been made public?
The public key is only capable of verifying the signature. It can't actually
sign anything. This is the whole point of signature cryptography. Anyone can
verify, but only one person can sign. If you could figure out the private key
from the public key, then it wouldn't be good cryptography.
> The public key you cannot remove?
The software that checks for a signature is in a ROM. You cannot change it.
