Rating: 3.0

JVM</span>(rev, 25 points)

"Bytecodes everywhere, reverse them."


In the zip file there was a .class file. It can be immediately recognized that this is a Java .class file (the name of the challenge "JVM" is also a hint as it stands for "Java Virtual Machine"), and while the .class file is just the binary, Java (like C# or VB.NET) can easily be decompiled because of how highly detailed the bytecode is. Pop this into a decompiler such as http://www.javadecompilers.com/, and we'll get the following source:

public class EKO {
    public static void main(String[] arrstring) {
        int n = 0;
        for (int i = 0; i < 1337; ++i) {
            n += i;
        String string = "EKO{" + n + "}";

If we run the source, we'll get our flag.

<span>Flag: EKO{893116}</span>

Original writeup (http://specterdev.blogspot.ca/2016/10/write-up-ekoparty-2016-ctf-reverse.html).