Android/JVM difference in RSA decryption

Question

I am trying to decrypt a String, that I have encrypted elsewhere. Here is my code:

private void test() {

    try {
        String stringMessage=\"Sf3O7Lr2+W         


        

Answer 1

Thanks to GregS's help in the comments. This is the solution that worked for me.

private void test() {

            try {
                String stringMessage="GEQRpAPA577ks/QveudNkk7H9DjItKGLDYW6xhH1YJGabCVzrkejkBh6S+APwEXxB84UV/q0sO5rqkgXWONJQ8CoMTfqXtUkAAwkYHSc86eGewkM8WpctA0AyNVFonOxDCXm84Uq8JRMzqskSH5VXHmMxvHIvpFgdhmt9Ir0cKWzoLsuvgfY9hfypfEyBXGZcoptQeKhsZxRGIlxbXhrFl/LqhC+F6vYtZ/j5pv2LUP38wh2rTCKnAQ+xvC+7wn5SVzt/Wbr/q7GjCoJuU9uFHQSS49KQDt+BzJL2XNwAMmdbC+XHYkEBBWxVSS+0hdSQxoaKVZZJk4hTnHwQlBAkw==";
                //Convert String back to Byte[] and decrpt
                byte[] byteMessage = Base64.decodeBase64(stringMessage.getBytes("UTF-8"));
                System.out.println("ENCRYPTED MESSAGE byte Length: "+byteMessage.length);

                String decryptedMsg = decryptString(byteMessage, loadCASPrivateKey());
                System.out.println(decryptedMsg);
            } catch (Exception e) {
                e.printStackTrace();
                return;
            }
        }

        private static String decryptString(byte[] message, Key privateKey) throws InvalidKeyException, NoSuchAlgorithmException, NoSuchPaddingException, IllegalBlockSizeException, BadPaddingException, UnsupportedEncodingException, NoSuchProviderException {
            Security.addProvider(new org.bouncycastle.jce.provider.BouncyCastleProvider());

            Cipher cipher = Cipher.getInstance("RSA/None/NoPadding","BC");
            cipher.init(Cipher.DECRYPT_MODE, privateKey);

            byte[] cipherData = cipher.doFinal(message);
            return new String(cipherData, "UTF-8");
        }

        private PrivateKey loadCASPrivateKey() throws IOException, NoSuchAlgorithmException, InvalidKeySpecException {
            InputStream is = getClass().getResourceAsStream( "/keys/app-private.key" );
            if (is == null) {
                System.out.println("NULL");
            }
            byte[] encodedPrivateKey = new byte[(int) 1216];
            is.read(encodedPrivateKey);
            is.close();

            // Generate KeyPair.
            KeyFactory keyFactory = KeyFactory.getInstance("RSA");

            PKCS8EncodedKeySpec privateKeySpec = new PKCS8EncodedKeySpec(encodedPrivateKey);
            PrivateKey privateKey = keyFactory.generatePrivate(privateKeySpec);

            return privateKey;

        }

Answer 2

It is possible your feeding the KeyFactory garbage since you are reading into a 2000 byte array, and your key is probably something like 128 (1024 bits) or 256 (2048 bits) bytes long. Additionally, you shouldn't really use RSA for encryption directly: there are security issues with this the data size you can encrypt is limited by the RSA key size.