You want to authenticate requests to event listeners created by the source server application.

When using a server application to make API calls to the SAP Customer Data Platform, you can authenticate requests to event listeners by passing a constructed JWT as the bearer token or by using the user key and secret key as parameters. The use of an asymmetric RSA key pair is also mentioned, which is typically involved in the creation of a JWT. However, passing the SSL certificate of the client or a one-time password generated by the REST API endpoint is not specified as a method for authenticating these requests.

References = The information is based on the SAP Customer Data Platform documentation, which details the methods for signing requests to the platform1.