The Legend Of Random

Introduction

In this tutorial we will be finishing up some last minute Olly things as we review a crackme. Well, sort of a crackme. It’s really just the program we used before but changed to ask for a serial number and displays either a good message if you get the serial right, or bad message if you get it wrong. I chose to do it this way, as opposed to jumping into a completely different crackme, because I want you to be able to focus on the serial checking routine, and not get bogged down in all off the other superfluous code. Next tutorial we will be going over a real crackme (I promise).

In this tutorial, all you need is OllyDBG (either my version or the original), and a copy of my revised crackme, which, by the way, I am calling the “First Assembly Kracking Engine”, or F.A.K.E. It is included in the files download for this tut. (and yes, Gdogg, I know kracking does not start with a ‘K’

You can download the files and PDF version of this tutorial on the tutorials page.

Let’s get started.

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What is Olly Debugger?

From the author, Oleh Yuschuk, “OllyDbg is a 32-bit assembler level analysing debugger for Microsoft® Windows®. Emphasis on binary code analysis makes it particularly useful in cases where source is unavailable. ” Olly is also a “dynamic” debugger, meaning it allows the user to change quite a few things as the program is running. This is very important when experimenting with a binary, trying to figure out how it works. Olly has many, many great features, and that is why it is probably the number one debugger used for reverse engineering (at least in ring 3, but we’ll get to that later.)

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What is reverse engineering?

Reverse engineering is the process of taking a compiled binary and attempting to recreate (or simply understand) the original way the program works. A programmer initially writes a program, usually in a high-level language such as C++ or Visual Basic (or God forbid, Delphi). Because the computer does not inherently speak these languages, the code that the programmer wrote is assembled into a more machine specific format, one to which a computer does speak. This code is called, originally enough, machine language. This code is not very human friendly,  and often times requires a great deal of brain power to figure out exactly what the programmer had in mind.

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