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 of the communication content as well as the sender?

A.
Message Authentication Code – MAC

B.
PAM – Pluggable Authentication Module

C.
NAM – Negative Acknowledgement Message

D.
Digital Signature Certificate

Explanation:
Message Authentication Code (MAC) is a keyed cryptographic hash function that is used for data integrity and
data origin authentication.
Incorrect Answers:
B: A pluggable authentication module (PAM) is used to integrate multiple low-level authentication schemes into
a high-level application programming interface (API).
C: A Negative Acknowledgement Message is a protocol message that is sent in many communications
protocols to negatively acknowledge or reject a previously received message, or to show some kind of error.
D: Digital Signature Certificate is an invalid term. Digital signatures and digital certificates are two different
security measures.

Harris, Shon, All In One CISSP Exam Guide, 6th Edition, McGraw-Hill, 2013, pp. 832
https://en.wikipedia.org/wiki/Pluggable_authentication_module
https://en.wikipedia.org/wiki/NAK_(protocol_message)
http://searchsecurity.techtarget.com/answer/The-difference-between-a-digital-signature-and-digital-certificate