What kind of key is used to encrypt credentials after they are decrypted on the MID Server?

The correct answer is the fixed Web Service key. In the context of ServiceNow Discovery and the role of the MID Server, the fixed Web Service key is utilized to maintain a consistent and secure methodology for encrypting credentials after they are decrypted during the discovery process.

This approach ensures that once the credentials are accessed by the MID Server, they can be encrypted again using a reliable and predefined key, which enhances security by preventing unauthorized access. The use of a fixed key allows for a standardized encryption process, facilitating easier management and auditing of access to sensitive information.

In contrast, other types of keys such as temporary access keys and randomly generated keys might change frequently or be designed for more transient scenarios, which can complicate the management of security for stored credentials. The user-provided key could also introduce variability and risk if not handled correctly, as it relies on the user to ensure the key is strong and secure. Thus, the fixed Web Service key is specifically intended for the reliable encryption of credentials within the ServiceNow Discovery framework.