Obtaining SAP Passport (Client Cert.) from SAP Trust Center 
Purpose
The Enterprise Portal provides an iView that allows users to request and receive an SAP Passport from the SAP Trust Center.
In this case, the Portal Server acts as a registration authority (RA), in other words, it verifies the users’ requests for a client certificate and confirms to the certification authority (CA) (in this case the SAP Trust Center) that the user is who he or she claims to be.
Prerequisites
You must register your Portal Server as a trusted RA with the SAP Trust Center. This is required so that, when the Trust Center receives a request for a client certificate from the Portal Server, it can verify the digital signature of the Portal Server in the request. To register your Portal Server with the SAP Trust Center, you must request a server certificate from the SAP Trust Center. This is described in
Obtaining a Server Certificate from SAP Trust Center.In addition, see the prerequisites for
Authentication Using Client Certificates.In particular: The Web servers must be configured to trust the Certification authority (CA) that issued the user certificates. In other words, you must import the root certificate of the SAP Trust Center into the keystore of the portal Web server (IIS). This is required so that the IIS can verify the user’s client certificate.
You must integrate the iView for requesting client certificates in a portal role, for example portal_user, so that all users can request a client certificate. This is the iView ClientSecurity.ClientCertInstall.
Process Flow
The following diagram describes what happens in the portal when a user requests a client certificate.

Note that the Portal Server acts as a registration authority (RA) in the above process. In other words, it confirms that the user requesting the certificate is who he or she claims to be.
Result
A SAP Passport is stored in the user's Web browser and can be used by the user for subsequent logons to the Enterprise Portal. Note that the user should subsequently log on using https otherwise the client certificate will be of no use.