Digital Signature (also make “nr” but now more private “c”)
Requirement: Bob wants to send the message to Sue only, but not all other associates.
1. Bob writes a message and encrypts it using his private key (he signs the message),
2. He then encrypts the resulting message with Sue’s public key (he makes it private to Sue),
3. Bob sends the twice-encrypted message to Sue over the Internet,
4. Sue receives and decrypts it twice, first with her private key and then with Bob’s public key.
5. Sue now can read the message.