- A
To encrypt the authorization code
Why wrong: PKCE does not encrypt the code; it uses a cryptographic challenge.
- B
To authenticate the end user
Why wrong: User authentication is handled by the authorization server, not PKCE.
- C
To ensure the client that requested the code is the same one redeeming it
The code verifier proves the client identity, preventing interception attacks.
- D
To generate the ID token
Why wrong: ID tokens are part of OIDC, not OAuth 2.0.
Question 284 of 1,000
CISSP Identity and Access Management Practice Question
This CISSP practice question tests your understanding of identity and access management. 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.
In an OAuth 2.0 authorization code flow with PKCE, what is the primary purpose of the code verifier and code challenge?
Clue words in this question
Noticing these words before you look at the options changes how you read each choice.
Clue:
"primary"Why it matters: Asks for the main purpose or function, not a secondary benefit. Eliminate answers that describe side-effects or partial functions.
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
✓
To ensure the client that requested the code is the same one redeeming it
PKCE (Proof Key for Code Exchange) prevents authorization code interception attacks, especially for public clients like mobile apps.
Key principle: Authentication proves identity; authorization controls what that identity can do after login. Both must work for full privileged access.
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
- ✗
To encrypt the authorization code
Why it's wrong here
PKCE does not encrypt the code; it uses a cryptographic challenge.
- ✗
To authenticate the end user
Why it's wrong here
User authentication is handled by the authorization server, not PKCE.
- ✓
To ensure the client that requested the code is the same one redeeming it
Why this is correct
The code verifier proves the client identity, preventing interception attacks.
Clue confirmation
The clue word "primary" in the question point toward this answer.
Related concept
Authentication checks who the user is.
- ✗
To generate the ID token
Why it's wrong here
ID tokens are part of OIDC, not OAuth 2.0.
Common exam traps
Common exam trap: authentication is not authorization
Logging in proves the user can authenticate. It does not automatically mean the user is allowed to enter privileged or configuration mode. Watch for AAA authorization, privilege level and command authorization details.
Detailed technical explanation
How to think about this question
This kind of question is testing the difference between identity and permission. A user may successfully log in to a router because authentication is working, but still fail to enter configuration mode because authorization is missing, misconfigured or mapped to a lower privilege level.
KKey Concepts to Remember
- Authentication checks who the user is.
- Authorization controls what the user is allowed to do after login.
- Privilege levels affect access to EXEC and configuration commands.
- AAA, TACACS+ and RADIUS can separate login success from command access.
TExam Day Tips
- Do not assume successful login means full administrative access.
- Look for words such as cannot enter configuration mode, privilege level, authorization or command access.
- Separate login problems from permission problems before choosing the answer.
Key takeaway
Authentication proves identity; authorization controls what that identity can do after login. Both must work for full privileged access.
Real-world example
How this comes up in practice
A developer is choosing between AES-256 (symmetric) and RSA-2048 (asymmetric) for encrypting a large file that will be sent to a partner. Symmetric encryption is fast but requires key exchange; asymmetric is slower but solves the key distribution problem. A hybrid approach — encrypt the file with AES, encrypt the AES key with RSA — is standard. Questions like this test whether you understand when each approach applies.
What to study next
Got this wrong? Here's your next step.
Review Cisco AAA concepts — authentication, authorization, and accounting. Study privilege levels (0–15), command authorization under TACACS+, and how RADIUS differs. Then practise related CISSP questions on access control and AAA configuration.
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Identity and Access Management — study guide chapter
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FAQ
Questions learners often ask
What does this CISSP question test?
Identity and Access Management — This question tests Identity and Access Management — Authentication checks who the user is..
What is the correct answer to this question?
The correct answer is: To ensure the client that requested the code is the same one redeeming it — PKCE (Proof Key for Code Exchange) prevents authorization code interception attacks, especially for public clients like mobile apps.
What should I do if I get this CISSP question wrong?
Review Cisco AAA concepts — authentication, authorization, and accounting. Study privilege levels (0–15), command authorization under TACACS+, and how RADIUS differs. Then practise related CISSP questions on access control and AAA configuration.
Are there clue words in this question I should notice?
Yes — watch for: "primary". Asks for the main purpose or function, not a secondary benefit. Eliminate answers that describe side-effects or partial functions.
What is the key concept behind this question?
Authentication checks who the user is.
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Last reviewed: Jul 4, 2026
This CISSP practice question is part of Courseiva's free ISC2 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 CISSP exam.
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