CAS-004 Security Engineering Practice Question
A security auditor is reviewing the cryptographic controls of a financial application that processes transactions. The application uses digital signatures with RSA 4096 and SHA-256. The auditor recommends migrating to a stronger algorithm due to concerns about long-term security and quantum resistance. Which of the following would be the MOST appropriate replacement?
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
Ed25519 offers strong security, smaller keys, and better performance than RSA. It is also resistance to some side-channel attacks. While not quantum-resistant, it is a forward-looking choice. ECDSA P-384 is also strong but larger key sizes. SHA-3 is a hash function, not a signature algorithm.
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
- ✗
SHA-3
Why it's wrong here
SHA-3 is a hash function, not a signature algorithm.
- ✓
Ed25519
Why this is correct
Ed25519 is a modern, secure signature algorithm with good performance and smaller key size.
- ✗
ECDSA P-521
Why it's wrong here
P-521 provides high security but is less commonly used and may have compatibility issues.
- ✗
ECDSA P-256
Why it's wrong here
P-256 has a smaller key size and may not be considered significantly stronger than RSA 4096.
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 |
Go deeper
Related to this question
About these practice questions
One of 968 original CAS-005 practice questions on Courseiva, each with a full explanation and wrong-answer analysis — not exam dumps or protected exam content. Learn why practice questions differ from exam dumps →
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.