Hi Anil,
You don't say your PI version. Check these links:
http://help.sap.com/saphelp_nw70/helpdata/EN/a4/d0201854fb6a4cb9545892b49d4851/frameset.htm
Examples for Using Digital Signatures - Integrating Security Functions - SAP Library
As you work with the java keystore, if you can install the in your java laptop the certificates, i think it would be similar than when they will be installed on PI (Import the Certificate as a Trusted Certificate (The Java™ Tutorials > Security Feat…)
Regards.