Method decrypt

examples/fixediv/java-simple/DecryptSimple.java:25–56

Decrypt CookieCloud data using standard Java crypto

(String uuid, String encrypted, String password)

     * Decrypt CookieCloud data using standard Java crypto
     */
    public static String decrypt(String uuid, String encrypted, String password) throws Exception {
        // 1. Generate key: MD5(uuid + "-" + password) first 16 chars
        String keyInput = uuid + "-" + password;
        MessageDigest md = MessageDigest.getInstance("MD5");
        byte[] hashBytes = md.digest(keyInput.getBytes(StandardCharsets.UTF_8));
        
        // Convert to hex string
        StringBuilder hexString = new StringBuilder();
        for (byte b : hashBytes) {
            String hex = Integer.toHexString(0xff & b);
            if (hex.length() == 1) hexString.append('0');
            hexString.append(hex);
        }
        String key = hexString.toString().substring(0, 16);
        
        // 2. Fixed IV: 16 bytes of zeros
        byte[] iv = new byte[16];
        
        // 3. Decode base64 encrypted data
        byte[] encryptedData = Base64.getDecoder().decode(encrypted);
        
        // 4. Create AES-128-CBC cipher
        SecretKeySpec keySpec = new SecretKeySpec(key.getBytes(StandardCharsets.UTF_8), "AES");
        IvParameterSpec ivSpec = new IvParameterSpec(iv);
        Cipher cipher = Cipher.getInstance("AES/CBC/PKCS5Padding");
        cipher.init(Cipher.DECRYPT_MODE, keySpec, ivSpec);
        
        // 5. Decrypt
        byte[] decrypted = cipher.doFinal(encryptedData);
        
        return new String(decrypted, StandardCharsets.UTF_8);
    }
    
    /**
     * Simple JSON value extractor (without external libraries)