using x.509 as authentication token to access BAPI using JCO

we are trying to access BAPI using JCO with x.509 certificate. The certificate is passed as a base64 encoded string. But are getting the following exception

Exception in thread "main" com.sap.conn.jco.JCoException: (103) JCO_ERROR_LOGON_FAILURE: Syntax error in received X.509-client certificate (base64-coding)

               connectProperties.setProperty(DestinationDataProvider.JCO_SYSNR, "01");

               connectProperties.setProperty(DestinationDataProvider.JCO_CLIENT, "500");     

                 connectProperties.setProperty(DestinationDataProvider.JCO_LANG, "en");             

               //createDestinationDataFile(connectionProperty, connectProperties);

               connectProperties.setProperty(DestinationDataProvider.JCO_X509CERT,certStr);

               destinationProvider.addDestination(connectionProperty, connectProperties);

               destinationProvider.registerDestinationProperty();

               JCoDestination destination = JCoDestinationManager.getDestination(connectionProperty);

               destination.getRepository();

could somebody help to fix this issue?