DEA-C01 Data Security and Governance Practice Question
Network Topology
Refer to the exhibit. A data engineer runs the AWS CLI command shown to encrypt a file using AWS KMS. The command succeeds. Later, the engineer tries to decrypt the file using the same key but without providing an encryption context. The decryption fails. What is the most likely reason?
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 encryption context must be provided during decryption.
When encrypting data with AWS KMS, an encryption context can be provided as additional authenticated data (AAD). This context must be supplied during decryption; otherwise, decryption fails. The command succeeded during encryption, so the key is not disabled (B is wrong) and the key policy is not the issue (A is wrong). File corruption would cause a different error (C is wrong).
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 KMS key policy does not allow decryption.
Why it's wrong here
A restrictive key policy would deny decryption even with the correct encryption context present, so it cannot explain a failure tied specifically to omitting that context. Key-policy review applies when a principal lacks kms:Decrypt permission for all attempts.
- ✗
The KMS key has been disabled.
Why it's wrong here
A disabled key would fail decryption regardless of whether the encryption context were supplied, yet the stem implies the context is the variable. Disabling keys is the right check when every operation using that key fails, not when only context-omitting calls do.
- ✗
The plaintext file was corrupted.
Why it's wrong here
Corruption would produce a generic integrity or ciphertext error, not the context-mismatch failure KMS reports when the supplied encryption context differs from the one bound at encryption. Corruption checks suit files damaged in transit or storage, where decryption fails irrespective of context.
- ✓
The encryption context must be provided during decryption.
Why this is correct
The encryption context supplied during encryption is cryptographically bound to the ciphertext, so KMS requires the identical key-value pairs to authorise decryption. Omitting them causes the request to fail, satisfying the stem's constraint that the same key alone is insufficient.
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JA
Written by Johnson Ajibi, MSc IT Security
Senior Network & Security Engineer · founder of Courseiva
This DEA-C01 practice question is part of Courseiva's free Amazon Web Services 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 DEA-C01 exam.