For initial authentication at the ABAP front-end server and authentication for search requests at the ABAP back-end server (fact sheets), you can use different authentication methods, including X.509 certificates. If you want to use X.509 certificates, you must set up a trusted relationship between SAP Web Dispatcher and the Internet Communication Manager (ICM) of the relevant ABAP servers.
For more information about the steps that are required to configure the trusted relationship, see:
For SAP NetWeaver 7.31: http://help.sap.com/nw731 .
For SAP NetWeaver 7.4:
For more information about authentication methods, see User Authentication and Single Sign-On.