简单注册器

最喜欢 Java 逆向了，反编译出来的真的很美观对吧

public void onClick(View v) {
    int flag = 1;
    String xx = editview.getText().toString();
    flag = (xx.length() == 32 && xx.charAt(31) == 'a' && xx.charAt(1) == 'b' && (xx.charAt(0) + xx.charAt(2)) + (-48) == 56) ? 0 : 0;
    if (flag == 1) {
        char[] x = "dd2940c04462b4dd7c450528835cca15".toCharArray();
        x[2] = (char) ((x[2] + x[3]) - 50);
        x[4] = (char) ((x[2] + x[5]) - 48);
        x[30] = (char) ((x[31] + x[9]) - 48);
        x[14] = (char) ((x[27] + x[28]) - 97);
        for (int i = 0; i < 16; i++) {
            char a = x[31 - i];
            x[31 - i] = x[i];
            x[i] = a;
        }
        String bbb = String.valueOf(x);
        textview.setText("flag{" + bbb + "}");
        return;
    }
    textview.setText("输入注册码错误");
}

关键代码就在于对 dd2940c04462b4dd7c450528835cca15 的处理，我们只需要将这段代码跑出来就知道了，很轻松对吧

x = list("dd2940c04462b4dd7c450528835cca15")

x[2] = chr(ord(x[2]) + ord(x[3]) - 50)
x[4] = chr(ord(x[2]) + ord(x[5]) - 48)
x[30] = chr(ord(x[31]) + ord(x[9]) - 48)
x[14] = chr(ord(x[27]) + ord(x[28]) - 97)

for i in range(16):
    a = chr(ord(x[31-i]))
    x[31 - i] = x[i]
    x[i] = a

print("flag{%s}" % "".join(x))

最后得出来的结果是 flag{59acc538825054c7de4b26440c0999dd}