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CAS-004 Practice Question: Is evaluating options for securing firmware…
A security engineer is evaluating options for securing firmware updates on IoT devices. Which TWO methods provide integrity verification of the update?
⚠ Common exam trap
CompTIA often tests the distinction between confidentiality and integrity, so candidates mistakenly select AES encryption (Option B) thinking it protects against tampering, when in fact encryption alone does not provide integrity verification.
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
✓
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. The firmware update's integrity is verified by recomputing the HMAC on the received data and comparing it to the transmitted tag; any tampering will cause a mismatch. This ensures that the firmware has not been altered in transit, providing integrity verification.
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
- ✗
Obfuscation of the firmware code
Why it's wrong here
Obfuscation is a weak form of intellectual property protection, not a cryptographic integrity check.
- ✗
AES encryption of the firmware
Why it's wrong here
Encryption provides confidentiality, not integrity; tampered data can still decrypt to garbage.
- ✓
Hash-based message authentication code (HMAC)
Why this is correct
HMAC uses a shared key to create a tag that verifies integrity and authenticity.
- ✓
Digital signature verification
Why this is correct
Digital signatures provide non-repudiation and integrity by using the manufacturer's private key.
- ✗
Secure Boot
Why it's wrong here
Secure Boot checks signatures at boot time, not during firmware update process.
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JA
Written by Johnson Ajibi, MSc IT Security
Senior Network & Security Engineer · founder of Courseiva
This CAS-005 practice question is part of Courseiva's free CompTIA 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 CAS-005 exam.