Principal propagation means the ability to forward the user context of a message unchanged from the sender to the receiver. It enables authentication of a message in the receiver system with the same user that issued the message in the corresponding sender system.

Thus, the receiver application is virtually part of the sender application, and the permissions and audit functions of the receiver application can be applied to the original user of the sender application.

Principal propagation is implemented using authentication between the involved messaging components. You can use SAP assertion tickets for this purpose.

More information: Configuring Principal Propagation Using the Advanced Adapter Engine