SNC Names, SSO, and User Mapping
Use
SNC Client Encryption is designed to enable secure communication between the client and SAP NetWeaver AS for ABAP. It is not designed to provide a single sign-on (SSO) solution. There is currently no technical hinderance to prevent someone from entering the SNC name used to secure the communication between a client and server into the SNC name field of of User Maintenance (transaction SU01). This is, however, a violation of the license agreement.
For single sign-on (SSO) scenarios, we offer SAP Single Sign-On. SAP Single Sign-On centralizes and greatly simplifies the way users log on to systems and applications in your IT landscape. Seamlessly integrated into your existing authentication processes, it offers enhanced security through state-of-the-art technology. But that is not the only benefit SAP Single Sign-On has to offer. Reduce your operating costs by eliminating password-related helpdesk calls, and improve user productivity - more than enough reasons to start thinking about implementing a single sign-on solution in your company.
For more information, seehttp://help.sap.com/sso.
More Information
SAP Note 1684886 
License conditions of SNC Client Encryption