APKrypt – Hack The Box¶

protected void onCreate(Bundle bundle) {
    super.onCreate(bundle);
    setContentView(R.layout.activity_main);
    this.b1 = (Button) findViewById(R.id.button);
    this.ed1 = (EditText) findViewById(R.id.editTextVipCode);
    this.b1.setOnClickListener(new View.OnClickListener() { // from class: com.example.apkrypt.MainActivity.1
        @Override // android.view.View.OnClickListener
        public void onClick(View view) {
            try {
                if (MainActivity.md5(MainActivity.this.ed1.getText().toString()).equals("735c3628699822c4c1c09219f317a8e9")) {
                    Toast.makeText(MainActivity.this.getApplicationContext(), MainActivity.decrypt("k+RLD5J86JRYnluaZLF3Zs/yJrVdVfGo1CQy5k0+tCZDJZTozBWPn2lExQYDHH1l"), 1).show();
                } else {
                    Toast.makeText(MainActivity.this.getApplicationContext(), "Wrong VIP code!", 0).show();
                }
            } catch (Exception e) {
                e.printStackTrace();
            }
        }
    });
}

public static String md5(String str) {
    try {
        MessageDigest messageDigest = MessageDigest.getInstance("MD5");
        messageDigest.update(str.getBytes());
        byte[] digest = messageDigest.digest();
        StringBuffer stringBuffer = new StringBuffer();
        for (byte b : digest) {
            stringBuffer.append(Integer.toHexString(b & 255));
        }
        return stringBuffer.toString();
    } catch (NoSuchAlgorithmException e) {
        e.printStackTrace();
        return "";
    }
}

public static String encrypt(String str) throws Exception {
    Key generateKey = generateKey();
    Cipher cipher = Cipher.getInstance("AES");
    cipher.init(1, generateKey);
    return Base64.encodeToString(cipher.doFinal(str.getBytes("utf-8")), 0);
}

public static String decrypt(String str) throws Exception {
    Key generateKey = generateKey();
    Cipher cipher = Cipher.getInstance("AES");
    cipher.init(2, generateKey);
    return new String(cipher.doFinal(Base64.decode(str, 0)), "utf-8");
}

private static Key generateKey() throws Exception {
    return new SecretKeySpec("Dgu8Trf6Ge4Ki9Lb".getBytes(), "AES");
}

public void onClick(View view) {
                try {
                    if (MainActivity.md5(MainActivity.this.ed1.getText().toString()).equals("735c3628699822c4c1c09219f317a8e9")) {
                        Toast.makeText(MainActivity.this.getApplicationContext(), MainActivity.decrypt("k+RLD5J86JRYnluaZLF3Zs/yJrVdVfGo1CQy5k0+tCZDJZTozBWPn2lExQYDHH1l"), 1).show();
                    }