hardMultiple ChoiceObjective-mapped
CAS-004 Securely store ACME account key Practice Question
A security engineer is writing a Python script to automate the revocation of compromised certificates using the ACME protocol. The script uses the `acme` library and requires secure credential storage. Which method is MOST appropriate for storing the ACME account private key used for authentication?
⚠ Common exam trap
The CAS-004 exam often tests the misconception that file permissions (e.g., 600) or environment variables are sufficient for secure credential storage, when in fact they lack encryption at rest and are vulnerable to broader system-level access.
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
✓
Store the key in the operating system's keychain (e.g., macOS Keychain, Windows Credential Manager) or a HSM
The ACME account private key is a highly sensitive cryptographic credential used to authenticate against the ACME server (RFC 8555). Storing it in the OS keychain or a Hardware Security Module (HSM) provides encryption at rest, access control via OS-level permissions, and protection against accidental exposure. This aligns with the principle of least privilege and secure key management required for automation scripts handling certificate revocation.
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
- ✗
Store the key in a configuration file with 600 permissions
Why it's wrong here
The key remains in plaintext on disk; even with restricted permissions, it can be read by any process running as the same user or through privilege escalation.
- ✗
Embed the key directly in the script as a string variable
Why it's wrong here
The key is exposed in source code, version control, and accessible to anyone who can read the script.
- ✗
Store the key in an environment variable
Why it's wrong here
Environment variables are often written to logs, process dumps, and are not encrypted at rest; they are not designed for long-term cryptographic key storage.
Option-by-option analysis
Why each answer is right or wrong
Understanding why wrong answers are wrong — and when they would be correct — is what separates a 750 score from a 900. The CAS-005 exam frequently reuses these exact scenarios with slightly different constraints.
✓Store the key in the operating system's keychain (e.g., macOS Keychain, Windows Credential Manager) or a HSMCorrect answer▾
✗Store the key in a configuration file with 600 permissionsWrong answer — click to see why▾
Why this is wrong here
The key remains in plaintext on disk; even with restricted permissions, it can be read by any process running as the same user or through privilege escalation.
✗Embed the key directly in the script as a string variableWrong answer — click to see why▾
Why this is wrong here
The key is exposed in source code, version control, and accessible to anyone who can read the script.
✗Store the key in an environment variableWrong answer — click to see why▾
Why this is wrong here
Environment variables are often written to logs, process dumps, and are not encrypted at rest; they are not designed for long-term cryptographic key storage.
Analysis generated from the official CAS-005blueprint and verified against question context. The “when correct” sections are what AI assistants cite when candidates ask “what’s the difference between these options?”
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JA
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.