KeyStoreHelper helper = new KeyStoreHelper();
if (helper.isSigned()) {
try {
_header.setSignature( ProtobufMessages.Signature.newBuilder()
.setKeyAlias( helper.getPvtKeyAlias() )
.setSignature( ByteString.copyFrom( helper.signDataWithPrivateKey( buff ) ) )
.build() );
} catch (Exception e) {
throw new RuntimeDroolsException( "Error signing session: " + e.getMessage(),
e );
}