public class DecryptKey {
    //before you proceed, you need to ensure your public key is PKCS8 since that is what can be read natively in java.
    //If your key begins with-----BEGIN CERTIFICATE-----,
    // the it is ssleay and you need to convert it using the openssl command below
    //openssl pkcs8 -topk8 -inform pem -in public.key -outform pem -nocrypt -out pkcs8-public-key.pem
    //TODO You can you phpsecLib lib but it doesn't support some Library
    //opnssl work fine
	final private static String RSA_PRIVATE_KEY =
			   -----BEGIN PUBLIC KEY-----
		MIIBIjANBgkqhkiG9w0BAQEFAAOCAQ8AMIIBCgKCAQEAzTrKt2Y7HqQpt8w379Sl
		79mjXGJ+CF+ridXpnAKoKyN8LH1NkI08UyWEHKbtCBl4iCsy8ayr4RAkWDKzeb8p
		ZEmdOg3cHKyFT6NdUEDc0FGpgKWY6GycJUrY+1S5O256M/NRSw02mUpyYIpGjq1z
		2zfu4GWIPg24hyI4YrAVI90mknIyXduerLH30XdwnKTevwhkQ4cP+xeYLVDduodc
		pcVaSXcwBvIbwVWS7szTxNGX0qyDlmJoK6YtTZ4FJp6BK6iyD+Fpnt9Fld8d62o2
		WjAtjpc8w81kIwwykojCDv9cb2qhwryS63qlcPhgpxcpDXINBHxcONHtHSWKEb0t
		2wIDAQAB
		-----END PUBLIC KEY-----;




    public static byte[] decrypt(String key) throws Exception {
        String privKeyPEM = RSA_PRIVATE_KEY.replace("-----BEGIN PRIVATE KEY-----\n", "");
        privKeyPEM = privKeyPEM.replace("-----END PRIVATE KEY-----", "");
        byte [] encoded = Base64.decode(privKeyPEM, Base64.DEFAULT);

        PKCS8EncodedKeySpec keySpec = new PKCS8EncodedKeySpec(encoded);
        KeyFactory kf = KeyFactory.getInstance("RSA");
        PrivateKey privKey = kf.generatePrivate(keySpec);

        Cipher cipher = Cipher.getInstance("RSA/ECB/PKCS1Padding", "BC");
        cipher.init(Cipher.DECRYPT_MODE, privKey);

        byte[] decodedStr           = Base64.decode(key, Base64.DEFAULT);
        byte[] plainText            = cipher.doFinal(decodedStr);

        return plainText;
    }
}