Which statement describes the computed authentication data in the AH protocol?
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A. B. C. D.C.
AH (Authentication Header) protocol is a security protocol that provides data integrity, authentication, and anti-replay protection for IP packets. It is one of the two protocols used in IPSec (the other one being ESP).
AH protocol generates authentication data which is used to authenticate the origin of the IP packet and to verify its integrity. The authentication data is computed based on the contents of the IP packet and the secret key shared between the sender and the receiver.
The answer to the question is C. The computed authentication data is part of the AH header. The AH header is added after the IP header and before the payload of the IP packet. The AH header includes the authentication data, which is a hash of the contents of the IP packet and the secret key. The authentication data is computed by applying a one-way hash function, such as HMAC-SHA1 or HMAC-SHA256, to the packet contents and the secret key.
The AH header also includes other fields, such as the Next Header field, which specifies the protocol type of the payload (e.g., TCP, UDP), and the Security Parameters Index (SPI) field, which is used to identify the security association (SA) to which the packet belongs.
Note that the computed authentication data is not sent across the network separately from the IP packet. It is included in the AH header, which is sent along with the IP packet. So, answer A is incorrect.
Answer B is also incorrect because the AH protocol does not create a new IP header. It adds an AH header after the existing IP header.
Answer D is also incorrect because the computed authentication data is not part of the original IP header. It is added in the AH header.