200-201 Security Concepts Practice Question
Which encryption method uses a single key for both encryption and decryption of data?
⚠ Common exam trap
Cisco often tests the distinction between symmetric and asymmetric encryption by presenting a scenario where a single key is used, and candidates may confuse 'single key' with the public key in asymmetric encryption, leading them to incorrectly select asymmetric encryption.
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
✓
Symmetric encryption
Symmetric encryption uses a single shared key for both encryption and decryption of data. This is the defining characteristic of symmetric algorithms like AES, DES, and 3DES, where the same secret key must be known to both sender and receiver to protect confidentiality.
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
- ✗
Asymmetric encryption
Why it's wrong here
Asymmetric uses a public/private key pair.
- ✓
Symmetric encryption
Why this is correct
Symmetric encryption uses one shared key.
- ✗
Digital signature
Why it's wrong here
Digital signatures use asymmetric encryption for authentication.
- ✗
Hashing
Why it's wrong here
Hashing is a one-way function, not encryption.
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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JA
Written by Johnson Ajibi, MSc IT Security
Senior Network & Security Engineer · founder of Courseiva
This 200-201 practice question is part of Courseiva's free Cisco 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 200-201 exam.