MITRE 2013 Writeup : Binary 200 #1

This one wasn't even a binary.  It was a JAR file that you disassembled to yield the following:

// Decompiled by Jad v1.5.8e. Copyright 2001 Pavel Kouznetsov.
// Jad home page: http://www.geocities.com/kpdus/jad.html
// Decompiler options: packimports(3)
// Source File Name:   Overrated.java

import java.io.PrintStream;
import java.security.MessageDigest;
import java.security.NoSuchAlgorithmException;
import java.util.Scanner;

public class Overrated
{

    public Overrated()
    {
    }

    public static void main(String args[])
    {
        String s = new String();
        String s1 = "3d38629f056c942d561b63dbe8e94653";
        Scanner scanner = new Scanner(System.in);
        for(; !encrypt(s).equals(s1); s = scanner.nextLine())
            System.out.print("Please enter the correct flag to continue: ");

        System.out.println("Good job!");
    }

    public static String encrypt(String s)
    {
        String s1 = "";
        try
        {
            MessageDigest messagedigest = MessageDigest.getInstance("MD5");
            messagedigest.reset();
            messagedigest.update(s.getBytes());
            byte abyte0[] = messagedigest.digest();
            String s2 = "";
            for(int i = 0; i < abyte0.length; i++)
            {
                String s3 = Integer.toHexString(0xff & abyte0[i]);
                if(s3.length() == 1)
                    s1 = (new StringBuilder()).append(s1).append("0").append(s3).toString();
                else
                    s1 = (new StringBuilder()).append(s1).append(s3).toString();
            }

        }
        catch(NoSuchAlgorithmException nosuchalgorithmexception) { }
        return s1;
    }
}

32-byte MD5.  Pull up your favorite hash cracker and set it up for an 8-byte bruteforce salted with MCA- and with the character set 0123456789ABCDEF:

elliptic@elliptic:~/hashcat-0.46$ ./hashcat-cli32.bin -m20 -a3 --custom-charset1=?dABCDEF --pw-min=8 --pw-max=8 hash.txt ?1?1?1?1?1?1?1?1
Initializing hashcat v0.46 by atom with 8 threads and 32mb segment-size...

Added hashes from file hash.txt: 1 (1 salts)
Activating quick-digest mode for single-hash with salt

NOTE: press enter for status-screen

3d38629f056c942d561b63dbe8e94653:MCA-:8EC28E12

All hashes have been recovered

Input.Mode: Mask (?1?1?1?1?1?1?1?1)
Index.....: 0/1 (segment), 4294967296 (words), 0 (bytes)
Recovered.: 1/1 hashes, 1/1 salts
Speed/sec.: - plains, 10.39M words
Progress..: 254333816/4294967296 (5.92%)
Running...: 00:00:00:24
Estimated.: 00:00:06:28

Started: Mon Jul 29 21:41:45 2013
Stopped: Mon Jul 29 21:42:09 2013
elliptic@elliptic:~/hashcat-0.46$

MCA-8EC28E12