In the scenario with financial documents, which action helps verify integrity of the document after approval?

• A. Encrypt with a public key
• B. Sign the document digitally
• C. Store in a secure server
• D. Hash the document to verify integrity

Answer: (D)

Integrity verification after approval is about catching any tampering by using a fingerprint of the document. A cryptographic hash creates a fixed-length digest that uniquely represents the exact content. If the document is changed in any way, re-hashing will produce a different digest. By generating and securely storing the original hash at the moment of approval, you can later re-hash the document and compare the two digests. A match confirms that the document’s content remains intact since approval.

Encryption with a public key protects confidentiality, not integrity checks by itself. A digital signature does verify integrity and authenticity, but hashing is the simplest, fastest way to perform a straightforward integrity check after approval—you can reuse it repeatedly to confirm the document hasn’t been altered. Storing the document in a secure server helps with protection and availability, but without a hash or signature, it doesn’t provide a direct way to verify that the content hasn’t changed since approval.