What does PKE have to do with digital signatures?
Digital signatures often use a public key encryption system. Consider Alice and Bob again: how can Bob be sure that it was really Alice who sent the message, and not the criminally-minded Eve pretending to be Alice? This is where digital signatures come in. Before encrypting the message to Bob, Alice can sign the message using her private key; when Bob decrypts the message, he can verify the signature using her public key. Here’s how it works: • Alice creates a digest of the message — a sort of digital fingerprint. If the message changes, so does the digest. • Sara then encrypts the digest with her private key. The encrypted digest is the digital signature. • The encrypted digest is sent to Bob along with the message. • When Bob receives the message, he decrypts the digest using Alice’s public key. • Bob then creates a digest of the message using the same function that Alice used. • Bob compares the digest that he created with the one that Alice encrypted. If the digests match, then B
