The SAP Authorization and Trust Management service is the central component in SAP BTP for managing application security. It facilitates application-to-service authentication by issuing JSON Web Tokens (JWTs) based on the OAuth 2.0 protocol. An application first authenticates itself to this service (e.g., using client credentials) and receives an access token. This token is then presented to the target service, which validates it to grant access, thereby securing the communication channel.

B. Alert Notification is a service for publishing and subscribing to alerts; it does not handle authentication for other applications or services.

C. The Cloud Connector is a proxy that establishes a secure tunnel between SAP BTP and on-premise systems, not for authentication between services within BTP.

D. Event Mesh is a messaging service for event-driven architectures. While it has security mechanisms, it is not the primary BTP service for general-purpose authentication.

1. SAP Help Portal, SAP Authorization and Trust Management Service, "What Is the SAP Authorization and Trust Management Service?". Section "Features" states it provides "OAuth 2.0 authorization server to secure applications and APIs".

2. SAP Help Portal, SAP Business Technology Platform Security, "Application Security". This guide details how the Authorization and Trust Management service (XSUAA) is used to issue tokens for business users and for technical communication (service-to-service).

3. SAP Help Portal, Developing Applications in the Cloud Foundry Environment, "Protecting Your Application". The documentation explicitly describes using the Authorization and Trust Management service to secure applications and their communication with other services.