Quick Answer
The answer is OAuth 2.0 tokens and API keys. OAuth 2.0 provides delegated, scoped access by issuing bearer tokens—typically JSON Web Tokens—that the client presents in the Authorization header, allowing the API server to validate requests without exposing user credentials, as defined in RFC 6749. API keys, on the other hand, are simpler static identifiers passed in headers or query parameters, used to authenticate the calling application rather than a user. On the CompTIA SecurityX CAS-004 exam, this tests your understanding of stateless, scalable REST API security methods; a common trap is confusing basic authentication (which sends credentials in plaintext) with these two valid approaches. Remember the mnemonic “OAK” for OAuth and API Keys—both are valid, but OAuth is for delegated user access while API keys identify the client application itself.
This CAS-004 practice question tests your understanding of security engineering. 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 TWO of the following are valid methods for securing REST APIs? (Select TWO.)
LDAP binds
Why wrong: LDAP is a directory protocol, not an API security method.
OAuth 2.0 tokens
OAuth 2.0 is widely used for API authorization.
API keys
API keys are a common way to authenticate API requests.
SAML assertions
Why wrong: SAML is used for web SSO, not typically for REST API security.
Kerberos tickets
Why wrong: Kerberos is used in Windows domains, not REST APIs.
Answer choices
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
OAuth 2.0 tokens
OAuth 2.0 tokens (B) are a standard method for securing REST APIs by providing delegated, scoped access without exposing user credentials. The client presents a bearer token (typically a JSON Web Token) in the Authorization header, which the API server validates to authorize the request. This aligns with RFC 6749 and is widely adopted for stateless, scalable API security.
Key principle: Answer the scenario, not the keyword: identify the specific constraint before choosing the most familiar-sounding option.
Answer analysis
For each option: why learners choose it and why it is or isn't the right answer here.
LDAP binds
Why it's wrong here
LDAP is a directory protocol, not an API security method.
OAuth 2.0 tokens
Why this is correct
OAuth 2.0 is widely used for API authorization.
Related concept
Read the scenario before looking for a memorised answer.
API keys
Why this is correct
API keys are a common way to authenticate API requests.
Related concept
Read the scenario before looking for a memorised answer.
SAML assertions
Why it's wrong here
SAML is used for web SSO, not typically for REST API security.
Kerberos tickets
Why it's wrong here
Kerberos is used in Windows domains, not REST APIs.
Common exam traps
Cisco often tests the distinction between authentication and authorization protocols, leading candidates to select Kerberos or SAML because they are 'secure,' but they fail to recognize that REST APIs require stateless, lightweight token-based mechanisms like OAuth 2.0 or API keys.
Detailed technical explanation
OAuth 2.0 tokens can be opaque (reference tokens) or self-contained (JWT), with the latter allowing the API to validate claims (e.g., expiry, scopes) without a database lookup. API keys (C) are simpler but less secure because they are static, often sent as query parameters or headers, and lack granular scoping or rotation mechanisms, making them vulnerable to interception and replay. In practice, many APIs combine both: API keys for client identification and OAuth 2.0 tokens for user authorization.
Key takeaway
Answer the scenario, not the keyword: identify the specific constraint before choosing the most familiar-sounding option.
Real-world example
A junior network technician can log in to a core router but cannot reach the enable prompt or configuration mode. The AAA server is authenticating the login — but the authorisation policy only grants privilege level 1, not 15. Authentication (who you are) is working; authorisation (what you can do) is not.
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FAQ
Security Engineering — This question tests Security Engineering — Read the scenario before looking for a memorised answer..
The correct answer is: OAuth 2.0 tokens — OAuth 2.0 tokens (B) are a standard method for securing REST APIs by providing delegated, scoped access without exposing user credentials. The client presents a bearer token (typically a JSON Web Token) in the Authorization header, which the API server validates to authorize the request. This aligns with RFC 6749 and is widely adopted for stateless, scalable API security.
Identify which exam domain this question belongs to, review the core concept, then practise similar questions from the same domain.
Read the scenario before looking for a memorised answer.
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Last reviewed: Jun 11, 2026
This CAS-004 practice question is part of Courseiva's free CompTIA 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 CAS-004 exam.
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