What is a Hashed Message Authentication Code (HMAC)?
A.
Encrypting a hash with a symmetric cipher
B.
Encrypting a hash with an asymmetric cipher
C.
A message digest
D.
A checksum
Explanation:
Answer A is correct; a Hashed Message Authentication Code is a hash encrypted with a preshared symmetric key.Incorrect Answers and Explanations: B, C, and D: Answers B, C, and D are incorrect. A digital signature encrypts a hash with an asymmetric cipher. A message digest is another name for a hash. A checksum is a simple hash.
HMAC’s result is a message digest, fingerprint, fixed-length hash value or simply a hash. This hash is an output and once it is generated it isn’t processed anymore. So you cannot speak of “encrypting a hash” (whatever that means). Such a statement implies that the hash is an input or some kind of intermediate result, which it is not. It is maybe better to rephrase answer A into “creating a hash with a symmetric cipher” (and answer B likewise). Otherwise answer C is the best answer.
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