GSEC Cryptography Practice Question
A security team is deploying a new internal TLS certificate authority (CA) for service-to-service authentication. The CA private key must be protected, and the team wants to ensure that if the key is compromised, the attacker cannot forge certificates without detection. Which of the following is the MOST effective control to detect unauthorized certificate issuance?
⚠ Common exam trap
The trap here is assuming that stronger cryptographic keys or client-side pinning will detect a compromised CA, when detection requires an auditable record such as Certificate Transparency.
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 all issued certificates to an internal Certificate Transparency (CT) log.
Certificate Transparency logs create a verifiable record of all certificates issued by a CA. By publishing internal certificates to a CT log, the team can monitor for unexpected entries, which would indicate unauthorized issuance. This detective control is more effective than preventive measures like key size or pinning, which do not alert on forgery.
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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Enforce a minimum RSA key size of 4096 bits for the CA key pair.
Why it's wrong here
Increasing RSA key size strengthens resistance to brute-force attacks on the CA key, but it does not provide detection if the key is compromised and used to sign certificates. An attacker with the private key can still issue certificates silently. Key size is a preventive hardening measure, not a detective control for unauthorized issuance.
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Require Certificate Revocation List (CRL) checking on all clients.
Why it's wrong here
CRL checking allows clients to reject revoked certificates, which is useful after a compromise is discovered. It does not detect unauthorized issuance in the first place; an attacker-issued certificate remains valid until revoked. CRL checking is a reactive control that depends on prior detection, so it is not the most effective detective measure.
- ✓
Publish all issued certificates to an internal Certificate Transparency (CT) log.
Why this is correct
CT logs provide an append-only, publicly auditable record of issued certificates. Publishing internal certificates to a CT log allows the security team to monitor for unauthorized issuance; any forged certificate would appear in the log, enabling detection. This is the most effective detective control among the options, as it directly addresses the risk of undetected certificate forgery.
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Configure certificate pinning in all client applications.
Why it's wrong here
Certificate pinning associates a service with a specific certificate or public key, preventing man-in-the-middle attacks using rogue certificates. However, it does not detect when the CA issues a certificate for a different service or an unauthorized certificate; it only protects clients that already pin. Pinning is a preventive control, not a detection mechanism for CA misuse.
About these practice questions
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JA
Written and reviewed by Johnson Ajibi, MSc IT Security
Senior Network & Security Engineer · founder of Courseiva
Last reviewed September 2026 · checked against the official GIAC exam blueprint
This GSEC practice question is part of Courseiva's free GIAC 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 GSEC exam.