What term describes a keyed hash used for integrity and authentication?

• A. MAC (Message Authentication Code)
• B. Initialization Vector (IV)
• C. Hash Function
• D. HTTPS

Answer: (A)

A MAC is the tool that provides both integrity and authentication with a secret key. It works by applying a MAC algorithm to the message using a shared secret key, producing a tag (the keyed hash). Anyone with the same key can verify the tag to confirm the message hasn’t been altered and that the sender is who they claim to be because only someone with the key could have created the correct tag.

Plain hash functions don’t use a secret key, so they can confirm that data hasn’t changed but can’t prove who sent it. An initialization vector is used to add randomness to encryption, not to verify integrity or authenticate. HTTPS is a secure web protocol that relies on TLS, not a single term for a keyed hash.