Message authentication code

Not to be confused with MAC addresses.

  • Add a secret to the end of each message that is also hashed. It is extremely unlikely that anyone who doesn’t know the secret to come up with an appropriate hash
  • Shared secret (this is a symmetric key)
  • Hash is computed not on message , but on
    • Bob sends message
    • Alice receives and computes
    • If , message is considered signed
  • Fast because asymmetric key crypto is not necessary