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CISSP Practice Question: Is designing a cryptographic solution to ensure…
A security engineer is designing a cryptographic solution to ensure data integrity and non-repudiation. Which combination should be used?
⚠ Common exam trap
Candidates often confuse 'asymmetric encryption' with 'digital signature,' thinking encryption alone provides non-repudiation, but encryption only provides confidentiality, while a digital signature specifically uses the private key for signing (not encryption) to achieve non-repudiation.
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 signature with hashing
Digital signature with hashing is the correct combination because hashing ensures data integrity by producing a fixed-size digest, and the digital signature encrypts that hash with the sender's private key, providing non-repudiation by proving the sender's identity and preventing denial of message origin. This satisfies both requirements without relying on a shared secret.
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
- ✗
HMAC with a shared key
Why it's wrong here
HMAC (Hash-based Message Authentication Code) uses a shared secret key to generate a tag that verifies both data integrity and message authenticity. While it confirms that the message originated from someone possessing the shared key and has not been tampered with, it cannot provide non-repudiation. Since both the sender and receiver share the same secret key, either party could have generated the HMAC, making it impossible to definitively prove to a third party who sent the message.
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Asymmetric encryption with digital signature
Why it's wrong here
Asymmetric encryption primarily provides confidentiality, ensuring that only the intended recipient can decrypt and read the message using their private key. While a digital signature, applied to a message hash, does provide integrity and non-repudiation, combining it with full asymmetric encryption of the entire message is often redundant and computationally inefficient if confidentiality is not the primary goal. The digital signature component alone, not the encryption of the message itself, is the mechanism that delivers integrity and non-repudiation.
- ✓
Digital signature with hashing
Why this is correct
This combination is the standard and correct approach for achieving both integrity and non-repudiation. First, the message is hashed to create a fixed-size digest, ensuring any alteration will change the hash. Then, this hash is encrypted with the sender's private key, creating the digital signature. This process guarantees integrity because the recipient can re-hash the message and compare it to the decrypted signature, and non-repudiation because only the sender's unique private key could have generated a valid signature.
- ✗
Symmetric encryption with HMAC
Why it's wrong here
Symmetric encryption provides confidentiality by scrambling data using a shared secret key, making it unreadable to unauthorized parties. HMAC, also utilizing a shared secret key, adds integrity and authenticity by verifying the message's origin and ensuring it hasn't been altered. However, because both the encryption and the HMAC rely on a key known to both sender and receiver, this combination fundamentally lacks non-repudiation, as neither party can undeniably prove to a third party that the other was the sole originator.
Go deeper
Related to this question
Learn chapter
Security Governance and Principles
Key term
Security
Security in IT is the practice of protecting systems, networks, and data from unauthorized access, damage, or theft.
Key term
Hashing
Hashing is a one-way mathematical function that converts any input data into a fixed-length string of characters, called a hash or digest, which is used to verify data integrity and store passwords securely.
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JA
Written by Johnson Ajibi, MSc IT Security
Senior Network & Security Engineer · founder of Courseiva
This CISSP 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 CISSP exam.