Is there a way to modify the contents of data being sent between two parties in such a way that the MAC verification algorithm will not detect the tampering?


1 Answer 1


Not if

  • a secure MAC is chosen (e.g., HMAC-SHA256, CBC-MAC)
  • the MAC is used correctly (e.g., not reusing a CBC-MAC key for encryption), and
  • the secret MAC key is unknown by the attacker

That's literally the entire point of a MAC.


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