CAS-004 Security Engineering Practice Question
A security architect is selecting a cipher suite for TLS 1.3 to ensure forward secrecy and high performance. Which cipher suite should be recommended?
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
✓
TLS_AES_256_GCM_SHA384
TLS 1.3 requires forward secrecy and uses AEAD ciphers. AES-256-GCM is a recommended AEAD cipher with strong security and performance.
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
- ✗
TLS_RSA_WITH_AES_256_CBC_SHA
Why it's wrong here
This uses RSA key exchange without forward secrecy and is not allowed in TLS 1.3.
- ✓
TLS_AES_256_GCM_SHA384
Why this is correct
Correct. This is a standard TLS 1.3 cipher suite providing forward secrecy and AEAD.
- ✗
TLS_DHE_RSA_WITH_AES_256_GCM_SHA384
Why it's wrong here
This is a TLS 1.2 cipher suite; TLS 1.3 does not use DHE explicitly but ECDHE.
- ✗
TLS_ECDHE_RSA_WITH_AES_128_CBC_SHA256
Why it's wrong here
Although it uses ECDHE for forward secrecy, this is a TLS 1.2 cipher suite, not TLS 1.3.
Quick reference
Symmetric Encryption Algorithm Comparison
| Algorithm | Key Size | Block Size | Status | Notes |
|---|---|---|---|---|
| AES-128 | 128-bit | 128-bit | Current standard | NIST approved; WPA3, TLS |
| AES-256 | 256-bit | 128-bit | Current standard | Preferred for sensitive / govt data |
| 3DES | 112-bit effective | 64-bit | Deprecated (2023) | Replaced by AES |
| DES | 56-bit | 64-bit | Broken | Cracked in < 24 h; never deploy |
| ChaCha20 | 256-bit | Stream cipher | Current | TLS 1.3, WireGuard |
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Written by Johnson Ajibi, MSc IT Security
Senior Network & Security Engineer · founder of Courseiva
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