Dennis replaces sensitive data in his database with unique identifiers. The identifiers allow him to continue to take actions on the data without exposing the data itself. What type of solution has he deployed?

Dennis has deployed a tokenization scheme. Encryption would require the data to be decrypted to be used, and this is not mentioned. Hashing could be used to conceal values but does not preserve the ability to work with the data. Masking modifies content to conceal personally identifiable information or other sensitive information.