PCNSA Decryption and Monitoring Practice Question
An organization is using outbound SSL decryption with a forward proxy. They notice that mobile devices (iOS/Android) are having trouble connecting to many HTTPS sites after decryption is enabled. IT has installed the root CA certificate on all devices. What is the most likely reason?
⚠ Common exam trap
Test-takers frequently assume installing the root CA certificate is sufficient for all devices, overlooking that mobile OSes enforce additional trust mechanisms like certificate transparency and pinning that are not bypassed by a locally installed root CA.
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
✓
The root CA certificate is not trusted by mobile OS due to certificate transparency or pinning.
Mobile operating systems (iOS and Android) implement certificate transparency (CT) requirements and certificate pinning for many HTTPS sites. Even if the root CA certificate is installed, the firewall's decryption certificate is not logged in public CT logs, causing the OS to reject the connection. Additionally, pinned certificates (e.g., for Google or Apple services) will fail validation when the firewall presents its own certificate instead of the original server certificate.
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
- ✗
The decryption profile does not allow TLS 1.3 connections.
Why it's wrong here
Most mobile sites support TLS 1.2; TLS 1.3 incompatibility would affect only a subset of sites.
- ✗
The firewall's decryption certificate uses a weak key length.
Why it's wrong here
Weak key length may cause browser warnings but not wholesale connection failures.
- ✓
The root CA certificate is not trusted by mobile OS due to certificate transparency or pinning.
Why this is correct
Mobile devices enforce CT or certificate pinning, causing the intercepted certificate to be rejected.
- ✗
The firewall is not configured to decrypt traffic from mobile devices.
Why it's wrong here
If traffic from mobile devices matched a no-decrypt rule, they wouldn't be affected by decryption.
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JA
Written by Johnson Ajibi, MSc IT Security
Senior Network & Security Engineer · founder of Courseiva
This PCNSA practice question is part of Courseiva's free Palo Alto Networks 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 PCNSA exam.