VA-003 Explain encryption as a service Practice Question
An application stores user profile documents in a database and must encrypt field values with Vault's transit engine. A reviewer notes that anyone with the application's token could still send arbitrary ciphertext to the decrypt endpoint and read the result. The team wants to limit blast radius if the token leaks. Which transit engine capability best reduces this risk?
⚠ Common exam trap
The trap here is treating audit logging as a preventive control, when it only records activity after a token has already succeeded in decrypting data.
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
✓
Use a Vault policy that grants only 'encrypt' capability on the key path, and issue decrypt rights to a separate, more tightly scoped identity.
The transit engine authorizes each endpoint path independently, so a token can be given encrypt-only rights. That means a leaked application token cannot decrypt stored ciphertext, and decryption can be reserved for a separate identity. Exporting keys or relying on post-hoc auditing does not prevent the misuse the reviewer described.
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
- ✗
Set a short TTL on the transit key so it expires and can no longer decrypt.
Why it's wrong here
Transit keys do not expire on a TTL the way tokens or leases do; key configuration controls rotation and versioning, not automatic expiry. Even if a key were disabled, that would break legitimate decryption for all callers rather than selectively limiting a leaked token. This does not address the leaked-credential scenario.
- ✗
Rely on the audit log to detect misuse after the fact and alert on decrypt calls from unexpected tokens.
Why it's wrong here
Audit logging provides detection and forensics but does not prevent a leaked token from successfully decrypting data in the moment. The reviewer's concern is limiting what the token can do if it leaks, which is an authorization problem; detection alone leaves the plaintext exposed before any alert fires.
- ✓
Use a Vault policy that grants only 'encrypt' capability on the key path, and issue decrypt rights to a separate, more tightly scoped identity.
Why this is correct
Transit capabilities are separated by endpoint, so a policy can allow 'encrypt' on the key's encrypt path while denying decrypt entirely. If the application's token leaks, the attacker can only produce ciphertext, not recover plaintext. Splitting decryption to a distinct identity with its own policy enforces least privilege and directly shrinks the blast radius.
- ✗
Enable 'exportable=true' so the team can move the key to a hardware security module and remove it from Vault.
Why it's wrong here
Exportable keys allow the raw key to be extracted, which increases exposure rather than reducing it, and moving encryption out of Vault removes the audit and policy controls that limit a leaked token. The requirement is to constrain what a stolen token can do, not to relocate key material.
Quick reference
AAA Protocol Comparison
| Protocol | Port(s) | Encryption | Transport | Primary Use |
|---|---|---|---|---|
| RADIUS | 1812 / 1813 | Password only | UDP | Network access control |
| TACACS+ | 49 | Full packet | TCP | Device administration |
| Diameter | 3868 | Full session | TCP / SCTP | Carrier / mobile networks |
| 802.1X | — | EAP-based | Layer 2 | Port-based access control |
TACACS+ encrypts the entire packet; RADIUS only encrypts the password field — a key exam distinction.
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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 HashiCorp exam blueprint
This VA-003 practice question is part of Courseiva's free HashiCorp 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 VA-003 exam.