200-201 Security Concepts Practice Question
Which of the following is an example of a symmetric encryption algorithm?
⚠ Common exam trap
Many exam-takers confuse hashing (SHA) and asymmetric algorithms (RSA, ECC) with symmetric encryption — candidates often assume any 'crypto-sounding' acronym is symmetric, but only AES among these uses a single shared key.
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
✓
AES
AES (Advanced Encryption Standard) is a symmetric encryption algorithm, meaning the same secret key is used for both encryption and decryption. It operates on fixed-size blocks (128 bits) with key sizes of 128, 192, or 256 bits and is the current NIST standard for symmetric encryption. Because both parties must share the same key, AES is fast and efficient for bulk data encryption.
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
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SHA-256
Why it's wrong here
SHA-256 is a cryptographic hash producing a fixed-length digest, not an encryption algorithm, and it uses no key at all. It is tempting because it appears alongside encryption primitives in security tooling, and would be the right choice for verifying integrity or storing password digests.
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RSA
Why it's wrong here
RSA is asymmetric, using a public key to encrypt and a separate private key to decrypt, so it does not meet the single-shared-key requirement. It is tempting because RSA is ubiquitous in TLS and digital signatures, and would be correct for key exchange or signing.
- ✓
AES
Why this is correct
AES is a symmetric block cipher using the same secret key for encryption and decryption, satisfying the stem's requirement for a symmetric algorithm. Operating on 128-bit blocks with key sizes of 128, 192, or 256 bits, it contrasts with asymmetric algorithms such as RSA, which use separate public and private keys.
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ECC
Why it's wrong here
ECC is asymmetric, relying on a public-private key pair over an elliptic curve, so it fails the single-shared-secret requirement. It is tempting because ECC offers strong security with small keys in TLS and mobile contexts, and would be correct for key agreement or signatures.
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 |
About these practice questions
This 200-201 question is part of Courseiva's 968-question bank — original exam-style content with full explanations and wrong-answer analysis, never real exam questions or exam dumps. Learn why practice questions differ from exam dumps →
JA
Written and reviewed by Johnson Ajibi, MSc IT Security
Senior Network & Security Engineer · founder of Courseiva
Last reviewed September 2026 · checked against the official Cisco exam blueprint
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.