I'm trying to get my head around this scenario. I understand that a private key can be used for signing a message to provide authentication and public key can be used for encrypting and its corresponding private key can be used to decrypt it. I came across this scenario and Ive been trying to research why this scenario will not work:
Suppose I changed the protocol in Kaufman & Perlman Plausibile Deniability Based on Public Key Technology, so that Alice first signs S, and then encrypts with Bob's public key. So instead of sending [{S}Bob]Alice to Bob, she sends {[S]Alice}Bob. Will this work?(can Bob be sure that the message came from Alice, but not be able to prove it to a third party?.
Why is the latter scenario a problem? Cant Bob just firstly use his private key to decrypt {[S]Alice}Bob and then use a Alice public key to verify [S]?