# Card-On-File Data Inquiry

## Card-On-File Data Inquiry Authentication Method

### Two-Way SSL

As one of the security protocols, Visa Developer sandbox secures its connections with clients by means of Two-Way SSL (Mutual Authentication) method. Refer to the link below to quickly learn about how to get credentials to start building with Two-Way SSL.

Visit the [Two-way SSL Guide](https://developer.visa.com/pages/working-with-visa-apis/two-way-ssl) to learn more.

### Message Level Encryption

Message Level Encryption (MLE) is required for all Card-On-File Data Inquiry implementations. MLE provides an enhanced security for message payload by using asymmetric encryption technique (public-key cryptography). The Card-On-File Data Inquiry request body is expected to be encrypted and the response body from the API will be encrypted as per MLE. You can generate the encryption/decryption key pairs in the Sandbox, Certification, or Production environments. For details, refer to the [Message Level Encryption](https://developer.visa.com/pages/encryption_guide) Documentation.