The answer is to implement Online Certificate Status Protocol (OCSP) responders. This is correct because OCSP provides real-time certificate revocation checking by querying a dedicated responder, which returns an immediate "good," "revoked," or "unknown" status for each certificate, eliminating the latency and bandwidth issues of downloading and processing Certificate Revocation Lists (CRLs). On the CISSP exam, this scenario tests your understanding of PKI operational controls, specifically the trade-off between CRLs (periodic, batch-oriented) and OCSP (real-time, query-based). A common trap is choosing CRL distribution points, but remember that CRLs rely on refresh cycles that can leave a window of vulnerability—OCSP closes that window instantly. For the exam, use the memory tip: "OCSP is the on-demand cop checking a badge, while CRL is the posted wanted poster that gets updated only once a day."
CISSP Security Architecture and Engineering Practice Question
This CISSP practice question tests your understanding of security architecture and engineering. Compare every option against the stated constraints before choosing — the best answer satisfies all requirements, not just the most obvious one. 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 large organization needs to deploy a Public Key Infrastructure (PKI) for thousands of devices and users. A key requirement is the ability to revoke certificates in real time when a device is lost or compromised. Which solution is most appropriate?
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
✓
Implement Online Certificate Status Protocol (OCSP) responders.
OCSP provides real-time certificate status checking by querying an OCSP responder directly, eliminating the delays inherent in CRL distribution. This meets the requirement for immediate revocation verification when a device is lost or compromised, as the responder can return a 'revoked' status instantly without waiting for a CRL refresh cycle.
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.
✗
Deploy multiple hierarchical CAs and distribute CRLs periodically.
Why it's wrong here
CRLs are not real-time; there is a delay between revocation and distribution.
✗
Rely on certificate expiration only and do not implement revocation.
Why it's wrong here
Expiration is too slow; compromised certificates remain valid until expiration date.
✗
Use a single Certificate Authority (CA) with a large Certificate Revocation List (CRL).
Why it's wrong here
Large CRLs cause performance issues and delays in revocation propagation.
✓
Implement Online Certificate Status Protocol (OCSP) responders.
Why this is correct
OCSP allows real-time verification of certificate status.
Related concept
Read the scenario before looking for a memorised answer.
Common exam traps
Common exam trap: answer the scenario, not the keyword
The trap here is that candidates confuse periodic CRL distribution (which is batch-oriented and slow) with real-time revocation, or assume a single CA with a large CRL is sufficient, overlooking the scalability and latency issues that make OCSP the correct choice for immediate status checks.
Detailed technical explanation
How to think about this question
OCSP (RFC 6960) uses a request-response model where the client sends a serial number and the responder returns a signed response with 'good', 'revoked', or 'unknown' status. Real-time revocation can be achieved with OCSP stapling (TLS extension) where the server presents a time-stamped OCSP response during the handshake, reducing load on responders. In high-availability environments, OCSP responders are often deployed behind load balancers with replicated revocation databases to ensure sub-second response times.
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 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.
Security Architecture and Engineering — This question tests Security Architecture and Engineering — Read the scenario before looking for a memorised answer..
What is the correct answer to this question?
The correct answer is: Implement Online Certificate Status Protocol (OCSP) responders. — OCSP provides real-time certificate status checking by querying an OCSP responder directly, eliminating the delays inherent in CRL distribution. This meets the requirement for immediate revocation verification when a device is lost or compromised, as the responder can return a 'revoked' status instantly without waiting for a CRL refresh cycle.
What should I do if I get this CISSP 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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Question Discussion
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