CAS-004 Security Engineering Practice Question
During a penetration test, an assessor successfully exploits a timing side-channel attack to extract an ECDSA private key from a secure enclave. Which TWO mitigations should the development team implement to prevent such attacks? (Select TWO.)
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
✓
Implement constant-time cryptographic operations
Timing attacks exploit variations in execution time based on secret data. Constant-time algorithms ensure that execution time does not depend on secret inputs. Blinding techniques randomize the computation so that timing variations are independent of the secret. Using stronger algorithms like Ed25519 does not inherently prevent timing attacks; constant-time implementation is needed. Adding noise to operations can help but is less effective than constant-time. Disabling debug interfaces is not a direct mitigation for timing attacks.
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
- ✓
Implement constant-time cryptographic operations
Why this is correct
Constant-time code ensures execution time is independent of secret data, thwarting timing attacks.
- ✗
Add random delays to cryptographic operations
Why it's wrong here
Adding noise is less effective than constant-time algorithms; statistical analysis can still extract timing information.
- ✗
Disable debug interfaces on the secure enclave
Why it's wrong here
Disabling debug interfaces prevents debugging but does not mitigate timing side-channel attacks.
- ✓
Use blinding techniques for ECDSA signing
Why this is correct
Blinding randomizes the signature computation, making timing attacks harder.
- ✗
Replace ECDSA with Ed25519
Why it's wrong here
Ed25519 also requires constant-time implementation to prevent timing attacks.
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 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.