Which of the following BEST describes a function relying on a shared secret key that is used along with a hashing algorithm to verify the integrity…

A Message Authentication Code (MAC) is a cryptographic function that uses a symmetric (shared) secret key in conjunction with a message and a cryptographic algorithm (often a hash function, as in HMAC) to generate a small block of data, known as a tag. This tag is appended to the message. The recipient, who possesses the same shared secret key, can re-compute the tag from the received message and verify that it matches the one sent. This process confirms that the message has not been altered (integrity) and that it originated from a party who knows the secret key (authentication).

B. PAM - Pluggable Authentication Module: This is a framework for authenticating users to a system (e.g., logging into Linux), not for verifying the integrity and origin of a specific message in a communication.

C. NAM - Negative Acknowledgement Message: This is a control message (often abbreviated as NAK) in communication protocols used to indicate that data was received with errors, not a cryptographic security function.

D. Digital Signature Certificate: A digital signature provides integrity and authentication but relies on asymmetric cryptography (a private/public key pair), not a shared secret key as specified in the question.

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1. National Institute of Standards and Technology (NIST)

FIPS PUB 198-1

The Keyed-Hash Message Authentication Code (HMAC)

July 2008.

Page 1

Abstract: "This Standard specifies a keyed-hash message authentication code (HMAC)

a mechanism for message authentication using cryptographic hash functions. HMAC can be used to verify both the data integrity and the authentication of a message." This directly supports that a keyed-hash mechanism (a type of MAC) provides both integrity and authentication.

2. National Institute of Standards and Technology (NIST)

SP 800-38B

Recommendation for Block Cipher Modes of Operation: The CMAC Mode for Authentication

May 2005.

Page 1

Section 1

Introduction: "A message authentication code (MAC) is a cryptographic checksum on a data block that is generated by a symmetric key algorithm... A MAC can be used to provide an assurance of the integrity and the authenticity of a data block." This source defines a MAC and its dual purpose of ensuring integrity and authenticity using a symmetric (shared) key.

3. Pfleeger

C. P.

Pfleeger

S. L.

& Margulies

J. (2015). Security in Computing (5th ed.). Prentice Hall.

Chapter 12

Section 12.2

"Symmetric and Asymmetric Encryption": The text distinguishes between symmetric key systems (using a shared secret) for MACs and asymmetric key systems for digital signatures. It states

"A message authentication code... is a cryptographic function that

like a hash

produces a small

fixed-size output from a variable-size input... Unlike a hash

a MAC uses a secret key."

4. Kurose

J. F.

& Ross

K. W. (2017). Computer Networking: A Top-Down Approach (7th ed.). Pearson.

Chapter 8

Section 8.3

"Message Integrity and Digital Signatures": The text explains

"To perform message integrity

in addition to a hash function

Alice and Bob will need a shared secret key

s. This shared secret key... is known only to Alice and Bob... The resulting message integrity code is called a message authentication code (MAC)." This university-level textbook clearly describes the function of a MAC using a shared secret key.