CAS-004 Security Engineering Practice Question
An organization is implementing a PKI and wants to ensure that clients can quickly check if a certificate has been revoked without downloading a large list. Which protocol should be used?
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
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Online Certificate Status Protocol (OCSP)
OCSP (Online Certificate Status Protocol) allows clients to check the revocation status of a single certificate in real time without downloading a full CRL.
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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Certificate Revocation List (CRL)
Why it's wrong here
A CRL requires clients to download the full revocation list, which the scenario explicitly rules out. It is tempting because CRLs are the traditional, universally supported revocation mechanism, and would be correct where clients can tolerate periodic bulk downloads and no low-latency lookup is needed.
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Online Certificate Status Protocol (OCSP)
Why this is correct
OCSP returns a signed, per-certificate revocation status from a responder, so clients query one certificate rather than downloading and parsing an entire CRL. This satisfies the requirement for fast revocation checking without transferring a large list.
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Certificate Transparency (CT)
Why it's wrong here
Certificate Transparency provides append-only public logs of issued certificates; it does not answer revocation status queries. It is tempting because it concerns certificate lifecycle visibility, but it suits detecting mis-issued certificates, whereas OCSP returns revocation status without downloading a full CRL.
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Simple Certificate Enrollment Protocol (SCEP)
Why it's wrong here
SCEP handles certificate enrolment and renewal, not revocation status checking, so it cannot satisfy the fast revocation lookup requirement. It is tempting because SCEP genuinely automates issuing certificates to network devices, and would be the right choice when onboarding routers or appliances that need certificates provisioned at scale.
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JA
Written by Johnson Ajibi, MSc IT Security
Senior Network & Security Engineer · founder of Courseiva
This CAS-005 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-005 exam.