Exam CISSP topic 1 question 221 discussion

From a security professional perspective, the Authentication Header (AH) protocol used in Virtual Private Networks (VPNs) only provides integrity and authentication, not non-repudiation. Integrity ensures that the data has not been tampered with during transmission, and authentication provides proof of the sender's identity. However, AH does not provide proof that the sender actually sent the message, nor does it prevent the sender from denying having sent it. Non-repudiation requires an additional mechanism, such as digital signatures or timestamps, to provide irrefutable proof of message origin and integrity. Therefore, while sender authentication does contribute to non-repudiation, it is not sufficient by itself, and AH does not provide non-repudiation as an independent protection. But in the ISC2 Official Study Guide (9th Edition), it is many times mentioned that sender authentication helps to provide non-repudiation, as it ensures that the sender of a message cannot deny having sent it. Therefore, for the sake of the CISSP exam, the correct option is A.

The best answer according to CISSP is A, but it is not the most correct

A seems correct: Authentication Header (AH) is a security protocol used to protect data transmission over the internet. It provides authentication and data integrity verification, ensuring that the data sent between two networked devices is not modified in transit. AH works by using cryptographic authentication and integrity verification mechanisms, such as HMAC or SHA-1, to generate a message authentication code (MAC), which is added to the data packet. This MAC is then used to verify the authenticity and integrity of the data when it is received by the destination device.

CISSP Official Study Guide - "The IP security (IPsec) protocol provides a complete infrastructure for secured network communications. IPsec has gained widespread acceptance and is now offered in a number of commercial operating systems out of the box. IPsec relies on security associations, and there are two main components: 1- The Authentication Header (AH) provides assurances of message integrity and nonrepudiation. AH also provides authentication and access control and prevents replay attacks."

The AH protocol provides a mechanism for authentication only. AH provides data integrity, data origin authentication, and an optional replay protection service. Data integrity is ensured by using a message digest that is generated by an algorithm such as HMAC-MD5 or HMAC-SHA. Data origin authentication is ensured by using a shared secret key to create the message digest. Replay protection is provided by using a sequence number field with the AH header. AH authenticates IP headers and their payloads, with the exception of certain header fields that can be legitimately changed in transit, such as the Time To Live (TTL) field.

AH does not do any encryption or encapsulation, therefore the payload is sent in plain test. Hence no Privacy or Confidentiality. However AH does provide Integrity and Authenticity, which is Non-repudiation.

The IP Authentication Header (AH) might provide non-repudiation if used with certain authentication algorithms. The IP Authentication Header may be used in conjunction with ESP to provide authentication. Users desiring integrity and authentication without confidentiality should use the IP Authentication Header (AH) instead of ESP. https://datatracker.ietf.org/doc/html/draft-ietf-ipsec-esp-00

Answer is correct "The AH is a mechanism for providing strong integrity and authentication for IP datagrams. It can also provide non-repudiation, depending on which cryptographic algorithm is used and how keying is performed. (Cisco)"