🔐 K0 Encryption System - Developer Guide

1. Overview

This guide shows how to implement secure decryption using AES, XOR, and Base64.

The decode order is: Base64 → XOR → AES Decrypt → UTF-8

2. Why wrap constants inside methods?

• Protect keys from static analysis.
• Prevent direct access via bytecode inspection.
• Enable optional native code obfuscation later.

Copyprivate static String getAESKey() {
    return "your-16-byte-key";
}

private static String getAESIV() {
    return "your-16-byte-iv";
}

private static byte[] getXORKey() {
    return new byte[]{0x1A, 0x2B, 0x3C, 0x4D};
}

3. Java Decryption Logic

Copyprivate String decode(String input) {
    try {
        byte[] base64 = Base64.decode(input, Base64.NO_WRAP);
        byte[] xored = xor(base64);

        Cipher cipher = Cipher.getInstance("AES/CBC/PKCS5Padding");
        SecretKeySpec keySpec = new SecretKeySpec(getAESKey().getBytes(StandardCharsets.UTF_8), "AES");
        IvParameterSpec ivSpec = new IvParameterSpec(getAESIV().getBytes(StandardCharsets.UTF_8));
        cipher.init(Cipher.DECRYPT_MODE, keySpec, ivSpec);

        byte[] decrypted = cipher.doFinal(xored);
        return new String(decrypted, StandardCharsets.UTF_8);
    } catch (Exception e) {
        return "";
    }
}

private byte[] xor(byte[] data) {
    byte[] key = getXORKey();
    byte[] result = new byte[data.length];
    for (int i = 0; i < data.length; i++) {
        result[i] = (byte)(data[i] ^ key[i % key.length]);
    }
    return result;
}

4. How to encode values (Python)

Copyfrom Crypto.Cipher import AES
import base64

def xor(data, key):
    return bytes([b ^ key[i % len(key)] for i, b in enumerate(data)])

def encode(plaintext, aes_key, aes_iv, xor_key):
    cipher = AES.new(aes_key.encode(), AES.MODE_CBC, aes_iv.encode())
    pad_len = 16 - len(plaintext) % 16
    padded = plaintext + chr(pad_len) * pad_len
    encrypted = cipher.encrypt(padded.encode())
    xored = xor(encrypted, xor_key)
    return base64.b64encode(xored).decode()

# Example usage
print(encode("HelloWorld", "k9D2!7aL4#oXf2Qb", "Q8b@3nL6rV1eZ0pT", bytes([0x5A, 0x2D, 0x6F, 0x1C])))

5. Usage in your K0 Class

Copypublic String a = decode("Base64EncodedString1==");
public String b = decode("Base64EncodedString2==");

6. Security Tips

• ✅ Use R8/ProGuard with string encryption rules
• ✅ Never use static final for keys
• ✅ XOR keys can be project-specific
• ✅ Consider C++ native layer via JNI for maximum security