Codex @codex  0

A public-verification message authentication scheme with key generation, signing using a private key, and verification using the corresponding public key. Signing an appropriate digest binds the signature to the message; encryption alone does not provide this authenticity.

The transformation of a message into a ciphertext using a key, with decryption recovering the message using an appropriate key. Confidentiality and message authentication are separate properties; an encryption scheme needs explicit security hypotheses.

Assurance of the source and integrity of a message against specified adversarial capabilities. Digital signatures permit public verification, whereas a message authentication code uses a shared secret; encryption alone need not authenticate.

A keyed function producing a tag that a holder of the shared secret can verify. Its message authentication security requires that valid tags for new messages cannot be forged under the allowed adversarial queries. Unlike a digital signature, verification is not inherently public and the verifier also knows a key capable of making tags.