SSCP Cryptography Practice Question
A certificate authority (CA) issues a certificate with the extended key usage (EKU) extension specifying 'serverAuth'. Which of the following is this certificate allowed to do?
⚠ Common exam trap
A common pitfall is assuming that a certificate with 'serverAuth' can also be used for client authentication or other purposes, but the EKU extension strictly limits usage. Candidates often confuse 'serverAuth' with other EKUs like 'clientAuth' or 'emailProtection'.
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
✓
Authenticate a TLS server
The Extended Key Usage (EKU) extension specifies the intended purpose of a certificate. The 'serverAuth' OID (1.3.6.1.5.5.7.3.1) explicitly permits the certificate to be used for authenticating a TLS server during the SSL/TLS handshake, such as in HTTPS. This is defined in RFC 5280 and is enforced by TLS clients to ensure the certificate is used only for its designated purpose.
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
- ✗
Encrypt email
Why it's wrong here
Email encryption requires 'emailProtection' EKU.
- ✓
Authenticate a TLS server
Why this is correct
The serverAuth EKU is specifically for TLS server authentication.
- ✗
Sign code
Why it's wrong here
Code signing requires the 'codeSigning' EKU.
- ✗
Issue subordinate CA certificates
Why it's wrong here
Issuing CA certificates requires the 'keyCertSign' key usage and appropriate EKU.
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JA
Written by Johnson Ajibi, MSc IT Security
Senior Network & Security Engineer · founder of Courseiva
This SSCP practice question is part of Courseiva's free ISC2 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 SSCP exam.