You are creating a database that will store usernames and credit card numbers for an application. You need to recommend a solution to store and resuse the credit card numbers in the database. What…

Data encryption uses cryptographic algorithms to transform plaintext credit card numbers into ciphertext that can be decrypted back to the original value when needed by the application. This satisfies both the storage security requirement and the 'reuse' requirement, since the original credit card number can be recovered with the appropriate key. Columnar or field-level encryption in a database is a common implementation of this approach for sensitive PCI-DSS-regulated data.

Transparent Data Encryption (TDE) encrypts the entire database files at rest (data files, log files, backups), but data is automatically decrypted when read into memory, meaning credit card numbers are exposed in plaintext at the application/query layer without additional field-level protection.

Encrypting File System (EFS) is a Windows filesystem-level encryption feature that protects files on disk, but like TDE it operates at the storage layer and does not provide column- or field-level encryption for individual database values such as credit card numbers.

Data hashing is a one-way, irreversible process; a hash of a credit card number cannot be reversed to recover the original number, which violates the requirement to reuse (retrieve) the actual credit card number for transactions.