CAS-004 Security Engineering Practice Question
A company is deploying a new IoT device that must perform secure boot and verify the integrity of firmware updates. The device has limited processing power. Which cryptographic algorithm combination is MOST appropriate for verifying firmware signatures efficiently?
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
✓
Ed25519 with BLAKE3
Ed25519 offers high performance and small key sizes compared to RSA or ECDSA, making it ideal for resource-constrained devices.
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
- ✗
AES-256-GCM for signing
Why it's wrong here
AES is symmetric and not used for digital signatures.
- ✗
RSA-4096 with SHA-256
Why it's wrong here
RSA-4096 is computationally expensive for IoT devices.
- ✗
ECDSA P-384 with SHA-384
Why it's wrong here
P-384 provides strong security but is slower than Ed25519.
- ✓
Ed25519 with BLAKE3
Why this is correct
Ed25519 is fast and secure, and BLAKE3 is a high-speed hash, ideal for IoT.
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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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.