Which technique ensures message authentication without requiring public-key cryptography by using a secret key and a hash function?

Which technique ensures message authentication without requiring public-key cryptography by using a secret key and a hash function?

• A. HMAC
• B. Digital Signature
• C. Encryption
• D. MAC

Answer: (A)

The key idea is using a keyed hash to prove both integrity and authenticity without relying on public-key cryptography. HMAC is a specific construction that takes a secret key and a cryptographic hash function and outputs a tag. The receiver, who also shares the secret key, recalculates the tag for the received message and checks it against the transmitted tag. If they match, the message came from someone who knows the secret key and hasn’t been altered. This approach contrasts with digital signatures, which rely on public-key cryptography and provide non-repudiation, and with encryption, which primarily aims to hide content rather than verify who sent it. A hash-based MAC like HMAC uses the secret key together with a hash function to achieve message authentication, making it the correct choice for authenticating messages without public-key cryptography.

The key idea is using a keyed hash to prove both integrity and authenticity without relying on public-key cryptography. HMAC is a specific construction that takes a secret key and a cryptographic hash function and outputs a tag. The receiver, who also shares the secret key, recalculates the tag for the received message and checks it against the transmitted tag. If they match, the message came from someone who knows the secret key and hasn’t been altered.

This approach contrasts with digital signatures, which rely on public-key cryptography and provide non-repudiation, and with encryption, which primarily aims to hide content rather than verify who sent it. A hash-based MAC like HMAC uses the secret key together with a hash function to achieve message authentication, making it the correct choice for authenticating messages without public-key cryptography.