Cheat Engine

Buggy · Last edited by Buggy on Sun Feb 17, 2008 6:59 pm; edited 1 time in total

- Introduction -
WHAT IS A CRACKME?

- A crackme (often abbreviated by cm) is a small program designed to test a programmers reverse engineering skills.

They are programmed by other reversers to have a legal way to "crack" software.

Crackmes, Reversemes and Keygenmes have similar protection schemes and algorithms to those found in commercial protections. Also some crackmes are even harder than their commercial counterparts.

A Keygenme specifically is designed for the reverser to not only find the algorithm used in the application, but also write a small Keygen in the programming language of their choice.

Often anti-debugging and anti-disassemble routines are used to confuse debuggers or make the disassembly useless. Code-obfuscation is also used to make the reversing even harder.

But most crackmes are hard by design, not by long obfuscated code. Because most reversers solve crackmes for fun! That's the reason why most reversers define rules for their crackmes.
(Sourced by wikipedia)If you get it, let's start crack!

We'll crack with Abex' 1st crackme.
- downloads -
http://buggy.ufree.kr/1stabexcrackme.exe
http://buggy.ufree.kr/OllyDbg.zip
it's really really easy to crack for basic people.

can anyone make hard drive to cdrom drive? no one can't.
so let's run ollydbg.And see assembly codes.

then open abex' 1st crackme.

hmm let's see, i think they are message box in assembly.
and use API, "GetDriveTypeA" to compare harddisk(?).
there are many methods to crack but i'll use basic method. (> next)

that will jump to correct message. and let's change JE to JMP, or JE to JNE.
Tips : jump assemblies (?)
JE Jump if equal (==)
JZ Jump if zero (==0)
JNZ Jump if not zero (!=0)
JA Jump if above (>)
JNBE Jump if not below or equal
JNE Jump if not equal
JNB Jump if not below (not <)
JB Jump if below (<)
JC Jump if carry
JBE Jump if below or equal (<=)
JNA Jump if not above
JP Jump if parity
JNP Jump if no parity

IF YOU finished, click the button <debug>.(A triangle shaped)

wow great

ShurikeN · Posted: Sun Feb 17, 2008 5:07 am Post subject:

mmmm, shouldn't this be in the Crackme's section?

benlue · Moderator Reputation: 0 Joined: 09 Oct 2006 Posts: 2142

Yes it should.

Snootae · Posted: Sun Feb 17, 2008 5:53 am Post subject:

nice tut, shows a rough guide on how easy crackmes can be cracked, a good read

Buggy · Posted: Sun Feb 17, 2008 7:10 am Post subject:

oh sorry i got it

XxOsirisxX · Posted: Sun Feb 17, 2008 10:18 am Post subject:

I did understand it and all...

But, guess this looks like more a Walktrough than a tutorial.

You're not explaining nothing. Like..

How you find the address?
why change JE o JMP?
How you know it was JE the one that was redirecting the MsgBox?

You're not explaining nothing, you're just showing how to crack that one only. So Walktrough.

sponge · Posted: Sun Feb 17, 2008 6:40 pm Post subject:

or hook getdrivetype and return DRIVE_CDROM

Labyrnth · Moderator Reputation: 9 Joined: 28 Nov 2006 Posts: 6285

Yes it was meant to teach a basic cracking to make a no_cd.
The Api GetDriveType is what he should have been focusing on instead of guiding the crackme.

Buggy · Posted: Sun Feb 17, 2008 7:01 pm Post subject:

sorry sorry i added some and i wasn't good at teaching in english so i thought difficult and i didn't try to teach clearly.