A checksum is a detective control because it identifies errors or unauthorized changes in data by comparing the calculated checksum value with the expected value. This helps detect potential data corruption or tampering after the fact.

https://onlinelibrary.wiley.com/doi/pdf/10.1002/9781119199014.fmatter

In an implementation review of a new accounting system, reviewing data conversion results is critical to ensure that data from the old system has been accurately and completely migrated to the new system. Accurate data conversion is essential for the integrity and reliability of the accounting system.

A gap assessment is the best method for evaluating compliance with a new cryptographic regulatory requirement. It allows the IS auditor to compare the organization's current cryptographic controls and practices against regulatory expectations, identifying specific areas of noncompliance and required remediation actions.