How to decode Blowfish CFB cipher in java?

Question

Java

Unable to decode text correctly. Here is the code:

public void decode() {
        byte[] KeyData = {0x2f, 0x18, (byte) 0xf5, (byte) 0x96, (byte) 0xa2, 0x17, 0x18, 0x29};
        byte[] IV = {0x01, 0x3d, (byte) 0xcf, (byte) 0xe2, (byte) 0xe3, (byte) 0xf9, (byte) 0xdd, (byte) 0x81};
        SecretKeySpec KS = new SecretKeySpec(KeyData, "Blowfish");
        Cipher cipher = null;
        try {
            cipher = Cipher.getInstance("Blowfish/CFB/NoPadding");
        } catch (NoSuchAlgorithmException e) {
            e.printStackTrace();
        } catch (NoSuchPaddingException e) {
            e.printStackTrace();
        }

        byte[] ciphertext = hexToBytes("424749c1d3b497");

        // Decrypt
        try {
            cipher.init(Cipher.DECRYPT_MODE, KS, new javax.crypto.spec.IvParameterSpec(IV));
        } catch (InvalidKeyException e) {
            e.printStackTrace();
        } catch (InvalidAlgorithmParameterException e) {
            e.printStackTrace();
        }
        byte[] message = new byte[0];
        try {
            message = cipher.doFinal(ciphertext);
        } catch (IllegalBlockSizeException e) {
            e.printStackTrace();
        } catch (BadPaddingException e) {
            e.printStackTrace();
        }

        System.out.println("-- Decrypted -----------");
        System.out.println("HEX:\t " + bytesToHex(message));
        System.out.println("PLAIN:\t " + new String(message));
        
    }

public byte[] hexToBytes(String str) {
        if (str == null) {
            return null;
        } else if (str.length() < 2) {
            return null;
        } else {
            int len = str.length() / 2;
            byte[] buffer = new byte[len];
            for (int i = 0; i < len; i++) {
                buffer[i] = (byte) Integer.parseInt(str.substring(i * 2, i * 2 + 2), 16);
            }
            return buffer;
        }

    }

    public  String bytesToHex(byte[] bytes) {

        char[] hexChars = new char[bytes.length * 2];
        for ( int j = 0; j < bytes.length; j++ ) {
            int v = bytes[j] & 0xFF;
            hexChars[j * 2] = hexArray[v >>> 4];
            hexChars[j * 2 + 1] = hexArray[v & 0x0F];
        }
        return new String(hexChars);
    }

The result I get is this:
HEX: 37F8D5CEE036CD
PLAIN: 7����6�
and it should be like this:
HEX: 37363035353633
PLAIN: 7605563 You can
check what the result should be here: blowfish.online-domain-tools.com/run/? inputType=fr...
What's wrong?

Answer 1

I solved the problem by changing the line with the name of the algorithm and the mod to

cipher = Cipher.getInstance("Blowfish/CFB8/NoPadding");

Answer 2

If you have (your) working code and an emulator on the site, then start by finding out the logic of correctly and incorrectly decrypted bytes - whether they depend on IV, on the key, on the ciphertext; try with more decoding-guaranteed values ​​of all three of these values, for example, all zeros, all ones, etc.