class KeyStoreHelper {

    public byte[] signDataWithPrivateKey(byte[] data) throws UnrecoverableKeyException,
                                                     KeyStoreException,
                                                     NoSuchAlgorithmException,
                                                     InvalidKeyException,
                                                     SignatureException {
        if( pvtKeyStore == null ) {
            throw new RuntimeException( "Key store with private key not configured. Please configure it properly before using signed serialization." );
        }
        PrivateKey pvtkey = (PrivateKey) pvtKeyStore.getKey( pvtKeyAlias,
                                                             pvtKeyPassword );
        Signature sig = Signature.getInstance( "MD5withRSA" );
        sig.initSign( pvtkey );
        sig.update( data );
        return sig.sign();
    }

    public  KeyStoreHelper();

}