we going to create a web application on sharepoint online with app parts. One of the app part will call the public restful service to get payroll information from SAP(ERP).
We have created a web service which will call the SAP and will retrieve data and we are going to host the web service as public since it has to be called from Sharepoint Online site.
The issue was security. How can we securely call this service. How can we restrict other than sharepoint user should not call this web service.
Please guide me on this