Hello Jana,
SAP Single Sign-On product (license required) offers two solutions for secure authentication and SSO for non-SAP web applications:
1) SAML - As part of the SAP Single Sign-On product we offer a SAML Identity Provider and if your web solution is a SAML Service Provider, you can configure SSO based on SAML.
Here you will be able to find more details: What is SAML 2.0 - Identity Provider for SAP Single Sign-On and SAP Identity Management - SAP Library
2) X.509 client certificates - As part of the SAP Single Sign-On product we offer a Secure Login Server that issues short lived X.509 client certificates. If your non-SAP solution support standards X.509 client certificates you can configure secure authentication and SSO using our Secure Login Server X.509 certificates.
Here you will be able to find more details: System Overview - What Is Secure Login? - SAP Library
I hope this will e helpful,
Regards,
Donka Dimitrova