Quick Answer
The answer is HMAC, or Hash-based Message Authentication Code, because it provides authenticity and integrity without non-repudiation. HMAC works by combining a shared secret key with a cryptographic hash function, producing a fixed-size authentication tag that verifies both that the data came from a party possessing the key and that it has not been altered in transit. Since the same key is shared between sender and receiver, either party could generate the tag, meaning the receiver cannot prove the sender’s identity to a third party—hence no non-repudiation. On the Systems Security Certified Practitioner SSCP exam, this concept tests your understanding of when to choose symmetric-key methods over asymmetric ones; a common trap is confusing HMAC with digital signatures, which use public-key cryptography and provide non-repudiation. Remember the memory tip: “Shared key, no proof—HMAC for integrity and truth, but not for court.”
This SSCP practice question tests your understanding of cryptography. Read the scenario carefully and evaluate each option against the stated constraints before committing to an answer. After answering, compare your reasoning against the explanation and wrong-answer breakdown below. Once you have made your selection, read the full explanation to reinforce the concept and understand why each distractor is designed to mislead on exam day.
A software developer wants to ensure the authenticity and integrity of an API request but does not require non-repudiation. Which cryptographic method should be used?
Digital signature using RSA
Why wrong: Digital signatures provide non-repudiation, which is not needed.
Symmetric encryption with CBC mode
Why wrong: Encryption provides confidentiality, not authenticity.
Hash-based message authentication code (HMAC)
HMAC verifies authenticity and integrity without non-repudiation.
Elliptic curve Diffie-Hellman (ECDH)
Why wrong: ECDH is key exchange, not authentication.
Answer choices
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
Hash-based message authentication code (HMAC)
HMAC uses a shared secret key combined with a cryptographic hash function to produce a fixed-size authentication tag. This ensures both authenticity (the request came from a party knowing the key) and integrity (the data has not been altered) without providing non-repudiation, because the same key is shared between sender and receiver, so the receiver could also have generated the tag.
Key principle: Answer the scenario, not the keyword: identify the specific constraint before choosing the most familiar-sounding option.
Answer analysis
For each option: why learners choose it and why it is or isn't the right answer here.
Digital signature using RSA
Why it's wrong here
Digital signatures provide non-repudiation, which is not needed.
Symmetric encryption with CBC mode
Why it's wrong here
Encryption provides confidentiality, not authenticity.
Hash-based message authentication code (HMAC)
Why this is correct
HMAC verifies authenticity and integrity without non-repudiation.
Related concept
Read the scenario before looking for a memorised answer.
Elliptic curve Diffie-Hellman (ECDH)
Why it's wrong here
ECDH is key exchange, not authentication.
Common exam traps
ISC2 often tests the distinction between authentication/integrity (HMAC) and non-repudiation (digital signatures), leading candidates to incorrectly choose digital signatures when non-repudiation is explicitly not required.
Detailed technical explanation
HMAC is defined in RFC 2104 and uses a construction of the form HMAC(K, m) = H((K' ⊕ opad) || H((K' ⊕ ipad) || m)), where H is a cryptographic hash function like SHA-256. This design prevents length-extension attacks that affect plain hash-based MACs. In practice, API requests often include a timestamp and nonce in the HMAC input to prevent replay attacks, and the shared secret is typically stored in a secure vault or environment variable.
Key takeaway
Answer the scenario, not the keyword: identify the specific constraint before choosing the most familiar-sounding option.
Real-world example
A developer is choosing between AES-256 (symmetric) and RSA-2048 (asymmetric) for encrypting a large file that will be sent to a partner. Symmetric encryption is fast but requires key exchange; asymmetric is slower but solves the key distribution problem. A hybrid approach — encrypt the file with AES, encrypt the AES key with RSA — is standard. Questions like this test whether you understand when each approach applies.
What to study next
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FAQ
Cryptography — This question tests Cryptography — Read the scenario before looking for a memorised answer..
The correct answer is: Hash-based message authentication code (HMAC) — HMAC uses a shared secret key combined with a cryptographic hash function to produce a fixed-size authentication tag. This ensures both authenticity (the request came from a party knowing the key) and integrity (the data has not been altered) without providing non-repudiation, because the same key is shared between sender and receiver, so the receiver could also have generated the tag.
Identify which exam domain this question belongs to, review the core concept, then practise similar questions from the same domain.
Read the scenario before looking for a memorised answer.
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Last reviewed: Jun 30, 2026
This SSCP practice question is part of Courseiva's free ISC2 certification practice question bank. Courseiva provides original exam-style practice questions with explanations, topic-based practice, mock exams, readiness tracking, and study analytics to help learners prepare for the SSCP exam.
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