BTC address sign message - proving that your the owner of a specific btc address with using your private key to generate a signature. only way to recover acc here if its hack by providing a evidence that your btc address sign message is hook to that acc. a way to do it is provide an evidence that you already stake you btc address to one of the thread here and other user quoted it for future evidence.
PGP (Pretty Good Privacy) - preventing other people to use your identity to have a transaction or dealing with confidential information. more secure privacy when in term of conversations, emails by providing a encrypted message and the only one who can decrypt it is the owner of the pgp public key, cause his the only one has the private key. also you can do a sign message in pgp.
GPG (GNU Privacy Guard) - a GNU project and the modern version of pgp.
I think this is the correct observations.
It's useful know that these are all asymetrically done for the most part.
PGP hashing is done with a private key so the inevitable hash is someone's public key.
Signed messages with Bitcoin addresses sign the message with that address' private key but the message itself can be verified using the public key (as the public key gets used as a piece of data that the signature is applied to in order to return the message or a checksum of the message that can then be validated further - as I understand it).
GPG was also generated by MIT also.
