- A
Asymmetric encryption
Why wrong: Asymmetric uses a public/private key pair.
- B
Symmetric encryption
Symmetric encryption uses one shared key.
- C
Digital signature
Why wrong: Digital signatures use asymmetric encryption for authentication.
- D
Hashing
Why wrong: Hashing is a one-way function, not encryption.
Question 438 of 1,000
200-201 Security Concepts Practice Question
This 200-201 practice question tests your understanding of security concepts. Read the scenario carefully and evaluate each option against the stated constraints before committing to an answer. After answering, compare your reasoning against the explanation and wrong-answer breakdown below. Once you have made your selection, read the full explanation to reinforce the concept and understand why each distractor is designed to mislead on exam day.
Which encryption method uses a single key for both encryption and decryption of data?
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.
Key principle: Answer the scenario, not the keyword: identify the specific constraint before choosing the most familiar-sounding option.
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.
Related concept
Read the scenario before looking for a memorised answer.
- ✗
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.
Common exam traps
Common exam trap: answer the scenario, not the keyword
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.
Detailed technical explanation
How to think about this question
Symmetric encryption algorithms like AES (Advanced Encryption Standard) operate on fixed-size blocks (e.g., 128-bit) using modes such as CBC or GCM. The same key is used in both the encrypt and decrypt operations, which makes symmetric encryption much faster than asymmetric encryption for bulk data, but requires secure key exchange (e.g., via Diffie-Hellman or a pre-shared key). In real-world scenarios, TLS 1.3 uses symmetric encryption (e.g., AES-GCM) for the actual data transfer after an asymmetric handshake establishes the shared session key.
KKey Concepts to Remember
- Read the scenario before looking for a memorised answer.
- Find the constraint that changes the correct option.
- Eliminate answers that are true in general but not in this case.
TExam Day Tips
- Watch for words such as best, first, most likely and least administrative effort.
- Review why wrong options are wrong, not only why the correct option is correct.
Key takeaway
Answer the scenario, not the keyword: identify the specific constraint before choosing the most familiar-sounding option.
Real-world example
How this comes up in practice
A practitioner preparing for the 200-201 exam encounters this exact type of scenario on the job. The correct answer here is not the most general option — it is the best answer for the specific constraint described. Answer the scenario, not the keyword: identify the specific constraint before choosing the most familiar-sounding option. Real exam questions reward reading the full scenario before eliminating options, because the constraint defines which answer fits.
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 |
What to study next
Got this wrong? Here's your next step.
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FAQ
Questions learners often ask
What does this 200-201 question test?
Security Concepts — This question tests Security Concepts — Read the scenario before looking for a memorised answer..
What is the correct answer to this question?
The correct answer is: 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.
What should I do if I get this 200-201 question wrong?
Identify which exam domain this question belongs to, review the core concept, then practise similar questions from the same domain.
What is the key concept behind this question?
Read the scenario before looking for a memorised answer.
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Last reviewed: Jul 4, 2026
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.
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