SAP Identity Authentication: SSO from SCP Portal to On Premise

Hello!

• I've got a Cloud Platform Portal Website.
• Currently you have to LogIn using an S-User.
• If you open an On-Premise App, you have to login a second time, with your On-Premise Credentials.

My Goal is this: I want the Customers to be able to register themselfes, without having to use an S-User. Also that the Customer just has to Login ONCE, using the newly registered Credentials.

I've seen the "SAP Cloud Platform Identity Authentication" Service, but I'm not sure if this is 100% what I need.

Thank you!