Dear Siva,
You can implement single sign-on based on X.509 client certificates for AS ABAP (SNC) and for AS JAVA (SSL) using the Secure Login Server of our SAP Single Sign-On product (license required).
See here chapter 1.1.3.2 Workflow with X.509 Certificate Request Using Secure Login Server:
http://help.sap.com/download/sapsso/secure_login_impl_guide_en.pdf
Regards,
Donka Dimitrova