A data processing system is provided, which comprises receiving circuitry for receiving, from a requester, a request to use decrypted data obtained by decrypting encrypted data. Trusted execution circuitry provides a trusted execution environment. The trusted execution circuitry is configured to: securely store a policy, acquire a key within the trusted execution environment, where the key is associated with the decrypted or encrypted data, and respond to the request based on the policy and one or more characteristics of the requester.