hardMultiple Choice
ISC2 CC Practice Question: A security architect is designing a system that…
A security architect is designing a system that must ensure that a sender cannot later deny having sent a message. Which cryptographic mechanism should be implemented?
Answer choices
Why each option matters
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
✓
Digital signatures
Digital signatures provide non-repudiation by binding the sender's identity to the message using public key cryptography. The sender cannot deny because only they possess the private key used to sign.
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
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Symmetric encryption
Why it's wrong here
Symmetric encryption uses a shared secret key, so either party could have produced the ciphertext; it provides confidentiality, not proof of origin. It is tempting because it is fast and simple for bulk data protection, and it would be the right choice when the requirement is keeping message contents secret between two trusted parties.
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Access control lists
Why it's wrong here
Access control lists govern which principals may read or modify resources; they record authorisation state, not cryptographic proof binding a message to its sender. They are tempting because they are the standard mechanism for restricting resource access, and would be correct when the requirement is limiting who can reach a system or object.
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Hashing
Why it's wrong here
Hashing produces a fixed-length digest that verifies integrity, but anyone can compute the same digest, so it cannot bind a message to one sender. It is tempting because it detects tampering, and would be correct when the requirement is confirming that data has not been altered in transit or at rest.
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Digital signatures
Why this is correct
Digital signatures use the sender's private key to produce a value verifiable with their public key, binding the sender's identity to the message. This provides non-repudiation, the exact constraint in the stem, because only the private-key holder could have generated the signature, so the sender cannot later deny it.
Quick reference
Asymmetric Encryption Algorithm Comparison
| Algorithm | Key Exchange | Signatures | Equivalent Security Key | Notes |
|---|---|---|---|---|
| RSA-3072 | Yes | Yes | 128-bit | Widely deployed; slow for bulk data |
| ECDSA P-256 | No | Yes | 128-bit | Fast signatures; standard TLS certs |
| ECDH / ECDHE | Yes | No | 128-bit | Perfect forward secrecy in TLS 1.3 |
| DH / DHE | Yes | No | 128-bit (3072-bit key) | Replaced by ECDHE in modern TLS |
| Ed25519 | No | Yes | ~128-bit | SSH keys, modern PKI |
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Written by Johnson Ajibi, MSc IT Security
Senior Network & Security Engineer · founder of Courseiva
This CC 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 CC exam.