Question
What are message authentication codes (macs)?
Answers
A message authentication code (MAC) is an authentication tag (also called a checksum) derived by application of an authentication scheme, together with a secret key, to a message. MACs are computed and verified with the same key so they can only be verified by the intended receiver, unlike digital signatures. MACs can be categorized as

unconditionally secure,
hash functionbased,
stream cipherbased, or
block cipherbased.

Simmons and Stinson proposed an unconditionally secure MAC that is based on encryption with a onetime pad. The ciphertext of the message authenticates itself, as nobody else has access to the onetime pad. However, there has to be some redundancy in the message. An unconditionally secure MAC can also be obtained by use of a onetime secret key.   Your Comment




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