Cheat Engine

[Redouane]

Hello,

By trying to crack/register a dozen of programs, I've noticed that their behaviour differs :

First, I tried to set breakpoints on getDlgItemText and such (or searched for referenced strings), and then followed the code that gets executed when you click "register" with random registration details till I found a serie of checks (compares) and conditional jumps where the program jumps to the part that displays "Invalid serial" (jump taken), or to "registration successful" (it never gets there with wrong registration details), I patched the jump, and tried registering again, and here, noticed that :
1- All the programs show the "registration successful" message.
2- Some of them became correctly registered, even when I click "about", it shows "Registered to Redouane"
3- Some of them became correctly registered, but still kept displaying "Unregistered trial version" in the about window, no features were disabled.
4- Some of them weren't at all registered, I still had the "register option", and the extra features were still disabled.

(?) I want to understand how the 3/4 things work, is there any common practice that software developers use to do that?

(?) Also, are there any tips on how to understand the assembly code that checks if the key is valid or not? It's most of the time very difficult to keep track of things when you find many function calls, jumps, and various operations.

(?) What if I have a valid username + serial key, will it make it easier to understand the key generation code?

[++METHOS]

Go through Lena151's tutorials.

Targets are like chess games, pretty much always different. Some may perform multiple checks while others may not. Sometimes, additional work may be required to 'clean up' your work. If additional flags aren't being set properly, your software may work, but still say unregistered. Sometimes, it's just a matter of changing the text to whatever you want. Having the serial key may help, but if you don't understanding what you're seeing in assembly, or know where various checks are being performed and/or how to find them, then that additional help may be useless to you.

[Redouane]

[++METHOS]

Yep.

[STN]

http://reversewithme.blogspot.com/2012/10/why-lena151-tutorials-wont-teach-you.html

Lena is ANEL

[++METHOS]

I read that article a few years back. Although the point is obvious, and a matter of semantics more than anything else, I think the suggestion to disregard the Lena tutorials is wrong. Even as an RE purist, there are still things that can be learned. Most people just want to be able to crack programs at the end of the day. I don't think there are many people that can offer any legitimate justification for discrediting the Lena tutorials. I've yet to see any better over the years for cracking software.

[Redouane]

[atom0s]

I wouldn't say her tutorials are bad or not good for beginners. They are just not relevant to today's applications and protections. For the things made during the time of those tutorials, they were well suited. Protections at that time were basically UPX and PECompact. The most 'advanced' thing was SecuROM and even then at that time, bypassing it was as easy as resetting the debug port of the process. They had a valid place in the RE timeline, but yes, now they are a bit stale.

To me, people are just judging them in a bad way, comparing them to what we have today in terms of protections. It'd be better if they recommended something else vs. just saying they are horrible / shit. Let the tutorials have their place in the RE timeline of when they were fully relevant. There is no reason to make them seem like a waste of effort.

[zm0d]

[mgostIH]

[atom0s]

[mgostIH]

[++METHOS]

Whether you place importance on the tools, the language or anything else, like most things, it's really a matter of being able to understand the why and not just the how. And although a lot of the tutorials out there do not primarily focus on those things, they do cover those things to a point that you can hopefully start to understand them over time, with experience.

[atom0s]