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CAS-004 Practice Question: Is the primary purpose of implementing a public…
Which of the following is the primary purpose of implementing a public key infrastructure (PKI)?
⚠ Common exam trap
Many exam-takers confuse the primary purpose of PKI (binding identities to keys) with its common applications (e.g., code signing, VPN), leading them to select a specific use case rather than the foundational function.
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
✓
To bind public keys to identities through certificates for authentication and encryption.
The primary purpose of a Public Key Infrastructure (PKI) is to bind public keys to identities through digital certificates, enabling authentication, non-repudiation, and encryption. PKI uses Certificate Authorities (CAs) to issue and manage X.509 certificates, which associate a public key with a specific entity (e.g., a user or server) and are validated via certificate chains. This binding is essential for secure communications, such as TLS/SSL, where certificates authenticate the server and establish encrypted sessions.
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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To store and verify password hashes for user authentication.
Why it's wrong here
PKI does not directly handle password storage; that is handled by directory services.
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To sign software and files to verify integrity and origin.
Why it's wrong here
Code signing is an application of PKI, not its primary purpose.
- ✓
To bind public keys to identities through certificates for authentication and encryption.
Why this is correct
PKI's main role is to create a framework of trust where certificates link public keys to entities, enabling secure communications.
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To provide a secure method for remote access via VPN.
Why it's wrong here
VPNs often use PKI, but PKI is a general infrastructure, not solely for VPNs.
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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.