Verifying PGP Messages

Question

Is it possible to sort of verify a PGP message?

Alice sends a PGP Encrypted message to Bob.

I know Alice and Bob's public key, and I have their encrypted and plaintext message.

1. Can I confirm that the PGP Encrypted message is the same as the plaintext message without knowing any of their private key?

2. Can I confirm that the PGP Encrypted message is from alice or bob with only their public key?

Answer 1

No to both. Details:

1. PGP encrypts a random symmetric key with Bob's public key, and then uses that to encrypt the message. Since you don't have that key, you can't check to see if the plaintext and ciphertext correspond under it.
2. The public key of a message only reveals who can decrypt it. All you learn is that whoever encrypted it knew Bob's public key, which doesn't really narrow it down at all.