In IPsec, which protocol provides data integrity and authentication without encryption?

• A. AH
• B. ESP
• C. IKE
• D. ISAKMP

Answer: (A)

In IPsec, the protocol that provides data integrity and authentication without encrypting the payload is Authentication Header. It verifies that a packet came from the claimed source and that the data hasn’t been altered in transit by computing and validating a message authentication code over the IP packet. Importantly, it does not encrypt the payload, so there is no confidentiality.

By contrast, Encapsulating Security Payload is designed to provide confidentiality (encryption) and can offer integrity as well, but encryption is its primary role. The remaining options are used to establish and manage the security association and keys (IKE and ISAKMP) rather than to protect the payload with integrity/authentication directly.