- A
Re-issue all certificates from a different issuing CA without revocation
Why wrong: The original certificates remain valid unless revoked; re-issuing does not revoke them.
- B
Use OCSP to individually check and revoke each certificate
Why wrong: OCSP is for status checking, not bulk revocation; individually revoking thousands of certificates is inefficient.
- C
Publish a CRL from the compromised CA listing all certificates it issued
Publishing a CRL from the compromised CA marks those certificates as revoked, while the CA certificate remains valid for CRL issuance.
- D
Revoke the compromised CA certificate and issue a new CRL from the root CA
Why wrong: Revoking the CA certificate invalidates all certificates under that CA, which may be too broad if some certificates are still trusted.
CAS-004 Security Engineering and Cryptography Practice Question
This CAS-004 practice question tests your understanding of security engineering and cryptography. 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 reviewing a PKI deployment where the root CA is kept offline. The issuing CA signs certificates for internal applications. Recently, a subordinate CA was compromised, and the engineer needs to revoke all certificates issued by that CA. Which of the following is the most efficient method to revoke these certificates?
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
Publish a CRL from the compromised CA listing all certificates it issued
The best method is to use a CRL issued by the compromised CA, marking all its unexpired certificates as revoked. Revoking the CA certificate itself invalidates all certificates issued by it, including valid ones. Distributing a new CRL from the root CA would require the root to be online. Individual certificate revocation is inefficient.
Key principle: NAT direction and interface roles matter as much as the IP address mapping. Inside/outside designation controls which traffic is translated.
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
- ✗
Re-issue all certificates from a different issuing CA without revocation
Why it's wrong here
The original certificates remain valid unless revoked; re-issuing does not revoke them.
- ✗
Use OCSP to individually check and revoke each certificate
Why it's wrong here
OCSP is for status checking, not bulk revocation; individually revoking thousands of certificates is inefficient.
- ✓
Publish a CRL from the compromised CA listing all certificates it issued
Why this is correct
Publishing a CRL from the compromised CA marks those certificates as revoked, while the CA certificate remains valid for CRL issuance.
Related concept
Static NAT maps one inside address to one outside address.
- ✗
Revoke the compromised CA certificate and issue a new CRL from the root CA
Why it's wrong here
Revoking the CA certificate invalidates all certificates under that CA, which may be too broad if some certificates are still trusted.
Common exam traps
Common exam trap: NAT rules depend on direction and matching traffic
NAT is not only about the public address. The inside/outside interface roles and the ACL or rule that matches traffic are just as important.
Detailed technical explanation
How to think about this question
NAT questions usually test address translation, overload/PAT behaviour, static mappings and whether the right traffic is being translated. Read the interface direction and address terms carefully.
KKey Concepts to Remember
- Static NAT maps one inside address to one outside address.
- PAT allows many inside hosts to share one public address using ports.
- Inside local and inside global describe the private and translated addresses.
- NAT ACLs identify traffic for translation, not always security filtering.
TExam Day Tips
- Identify inside and outside interfaces first.
- Check whether the scenario needs static NAT, dynamic NAT or PAT.
- Do not confuse NAT matching ACLs with normal packet-filtering intent.
Key takeaway
NAT direction and interface roles matter as much as the IP address mapping. Inside/outside designation controls which traffic is translated.
Real-world example
How this comes up in practice
A small business has 20 workstations on the 192.168.1.0/24 network and one public IP from its ISP. The router uses PAT (NAT overload) so all 20 devices share one public address using different source ports. NAT questions test whether you understand the four address terms and which direction each translation applies.
What to study next
Got this wrong? Here's your next step.
Review the four NAT address types (inside local, inside global, outside local, outside global), PAT port overload, and static vs dynamic NAT use cases. Then practise related CAS-004 NAT questions on configuration and troubleshooting.
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Security Engineering and Cryptography — study guide chapter
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FAQ
Questions learners often ask
What does this CAS-004 question test?
Security Engineering and Cryptography — This question tests Security Engineering and Cryptography — Static NAT maps one inside address to one outside address..
What is the correct answer to this question?
The correct answer is: Publish a CRL from the compromised CA listing all certificates it issued — The best method is to use a CRL issued by the compromised CA, marking all its unexpired certificates as revoked. Revoking the CA certificate itself invalidates all certificates issued by it, including valid ones. Distributing a new CRL from the root CA would require the root to be online. Individual certificate revocation is inefficient.
What should I do if I get this CAS-004 question wrong?
Review the four NAT address types (inside local, inside global, outside local, outside global), PAT port overload, and static vs dynamic NAT use cases. Then practise related CAS-004 NAT questions on configuration and troubleshooting.
What is the key concept behind this question?
Static NAT maps one inside address to one outside address.
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Last reviewed: Jul 4, 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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