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57 terms starting with "M"

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Message Authentication Code

A short code attached to a message that lets a receiver verify both its integrity and that it came from someone holding a shared secret key, providing message authenticity without the asymmetry of digital signatures.

A message authentication code (MAC) is computed from the message and a secret key shared between sender and receiver, so the receiver can recompute it to confirm the message was not altered and was produced by a holder of the key. MACs provide integrity and authenticity using symmetric cryptography (cheaper than signatures) but require both sides to share a secret, so they cannot prove origin to third parties. HMAC is the most common MAC construction.

Introduced in: Cryptography Essentials

Examples

  • Verifying a message's MAC to confirm it was not altered in transit.
  • Using a MAC to authenticate messages between two parties.
  • Computing HMAC as a common MAC construction over a message.

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