The correct approach is implementing OAuth 2.0 with Bearer tokens over HTTPS, as this combination directly addresses both API authorization and tamper protection. OAuth 2.0 provides a robust framework for authorization by issuing scoped access tokens that verify a client’s identity and permissions, while HTTPS ensures the integrity and confidentiality of every request in transit through TLS encryption. On the CISSP exam, this question tests your understanding of the layered security model—specifically that authorization and integrity are distinct controls that must be combined. A common trap is confusing authentication with authorization: API keys authenticate a client but offer no tamper protection, and TLS alone secures the channel but does not control who can access the resource. Remember the mnemonic “OATH” for OAuth 2.0 over HTTPS: it provides Authorization, Tamper protection, and Honest transport.
CISSP Software Development Security Practice Question
This CISSP practice question tests your understanding of software development security. 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.
A security engineer is designing an API that handles sensitive customer data. The engineer wants to ensure that only authorized clients can access the API, and that requests are not tampered with in transit. Which approach best addresses both requirements?
Clue words in this question
Noticing these words before you look at the options changes how you read each choice.
Clue: "best"
Why it matters: Signals that multiple options may be partially correct. Choose the option that most directly solves the exact problem described, not the one that sounds most complete.
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
✓
Implementing OAuth 2.0 with Bearer tokens over HTTPS
Option D is correct because OAuth 2.0 provides authorization (access tokens) and when used over HTTPS, ensures integrity and confidentiality. Option A is wrong because API keys alone provide authentication but not tamper protection. Option B is wrong because TLS provides encryption but not authorization. Option C is wrong because HMAC provides integrity but not authorization.
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.
✗
Enforcing TLS for all communications
Why it's wrong here
TLS provides encryption and integrity but does not authorize which clients can access the API.
✗
Requiring a digital signature using HMAC on each request
Why it's wrong here
HMAC ensures integrity but does not provide authorization.
✓
Implementing OAuth 2.0 with Bearer tokens over HTTPS
Why this is correct
OAuth 2.0 provides delegated authorization, and HTTPS ensures confidentiality and integrity of tokens and data.
Clue confirmation
The clue word "best" in the question point toward this answer.
Related concept
Authentication checks who the user is.
✗
Using API keys transmitted in the request header
Why it's wrong here
API keys authenticate the client but do not protect against tampering if not combined with TLS.
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.
Related glossary terms
Concepts from this question explained
These glossary pages explain the core terms tested in this CISSP question in full detail.
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.
Software Development Security — This question tests Software Development Security — Authentication checks who the user is..
What is the correct answer to this question?
The correct answer is: Implementing OAuth 2.0 with Bearer tokens over HTTPS — Option D is correct because OAuth 2.0 provides authorization (access tokens) and when used over HTTPS, ensures integrity and confidentiality. Option A is wrong because API keys alone provide authentication but not tamper protection. Option B is wrong because TLS provides encryption but not authorization. Option C is wrong because HMAC provides integrity but not authorization.
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: "best". Signals that multiple options may be partially correct. Choose the option that most directly solves the exact problem described, not the one that sounds most complete.
What is the key concept behind this question?
Authentication checks who the user is.
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