Fediverse

Been forever since I did any work with cryptography, but if my memory is correct:

Alice needs Bob’s public key to verify a signed message from Bob haven’t been altered;

Bob needs Alice’s public key to encrypt a message that can only be decrypted by Alice;

If Bob sends Alice a message encrypted with Alice’s public key, signed with Bob’s private key, containing “Hello, how are you?” ; this message could be verified as authentic by Charlie using Bob’s public key but Charlie cannot see the contents of the message as Charlie does not have Alice’s private key.

Without Alice disclosing their private key, how can Charlie review the content of a reported message from Alice claiming Bob sent them something inappropriate?

I.e. how can Charlie be certain if Alice claims Bob sent “cats are evil” when Charlie cannot decrypt the original message, only verify the original message have not been altered via Bob’s public key.