A digital signature is a cryptographic function that provides integrity, authentication, data origin, and, in some cases, non-repudiation protections. Just like a hand-written signature, they are designed to be unique to the signer, that is, the individual or device responsible for signing the message and who possesses the signing key. Digital signatures come in two flavors, representing the type of cryptography in use: symmetric (secret, shared key) or asymmetric (private key is unshared).
The originator in the following diagram takes his message and signs it to produce the signature. The signature can now accompany the message (now called the signed message) so that anyone with the appropriate key can perform the inverse ...
