ITPEC FE Morning October 2019 Question 38
ITPEC FE Morning October 2019 — Question 38 of 80
Message Authentication Code (MAC) — purpose of message digest in MAC.
A message digest (hash) inside a MAC is used to verify that the message has not been altered or falsified during transmission — i.e., it ensures integrity.
The sender computes a hash over the message combined with a shared secret key and attaches the result. The receiver recomputes the hash using the same key and compares. If they match, the message was not tampered with.
Why not others:
- (a) MAC does not check which encryption method was used — it verifies integrity, not algorithm metadata
- (b) "Check the overview" is a meaningless distractor with no security relevance
- (d) Confidentiality is the job of encryption, not MAC — MAC does not hide message content
Key rule: MAC = integrity + authentication; Encryption = confidentiality.
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