Cheat Engine

nog_lorp · Posted: Sun Mar 04, 2007 10:51 pm Post subject: [crackme] My take on a crackme

Tell me what you think, and how hard you find it. If you get it right it will bell (the "wrong" message looks a little similar to the "right" message if you are just glancing).

The goal is to guess the number, which is input as an argument. The goal is not to get it to display the "correct" messag by patching it, thats easy as hell.

It is not packed and doesn't use any encryption.

Enjoy!
~nog_lorp

nog_lorp · Posted: Sun Mar 04, 2007 10:55 pm Post subject:

Crashes with no argument silly. I should have fixed that but I was lazy.

cracknog.exe guessnumber

And... damn x0r do you ever leave this forum? Don't you eat and stuff like that? Very Happy

nog_lorp · Posted: Sun Mar 04, 2007 11:15 pm Post subject:

Err... patching? The goal is to find the correct input, not patch it.

Ungreat · Posted: Sun Mar 04, 2007 11:29 pm Post subject:

This is my idea of a good time.

*censored user*: I think you just can't figure it out Razz

This algorithm looks liek a dummy to me Confused

Analyzing further though.

Nice job with this

nog_lorp · Posted: Sun Mar 04, 2007 11:31 pm Post subject:

Well, a little addition and subtraction, and lotsa bitwise operations Very Happy

. There are some fun tricks in there too. Try breaking somewhere in that algorithm and then restarting it Very Happy

.

~nog_lorp

EDIT: hehe, x0r = Irwin?

nog_lorp · Posted: Sun Mar 04, 2007 11:34 pm Post subject:

Nope. Try it Very Happy

. Although now that I think of it, I should have used the anti-break trick on that part too, just for added confusion.

~nog_lorp

john0312 · Posted: Sun Mar 04, 2007 11:35 pm Post subject:

SMN · Posted: Sun Mar 04, 2007 11:38 pm Post subject:

nog_lorp · Posted: Sun Mar 04, 2007 11:39 pm Post subject:

x0r: No, its not correct at all, sorry Sad

The solution will never be present in the program memory unless you enter it.

~nog_lorp
Edit: guy with monkey ass avitar: good, now trace back and find the right number to enter.

john0312 · Posted: Sun Mar 04, 2007 11:39 pm Post subject:

john0312 · Posted: Sun Mar 04, 2007 11:43 pm Post subject:

nog_lorp · Posted: Sun Mar 04, 2007 11:47 pm Post subject:

Wow, talk about love-hate! Got anything to say about the thread though? Very Happy

~nog_lorp

john0312 · Posted: Sun Mar 04, 2007 11:50 pm Post subject:

john0312 · Posted: Sun Mar 04, 2007 11:55 pm Post subject:

nog_lorp · Posted: Mon Mar 05, 2007 12:01 am Post subject:

(er, in reply to john's earlier post) Thanks. I made it all today, relearning all the C I've forgotten (and some new stuff, function pointers=yuck), ran into some snags with uber-shit libraries (rand() increases by 2-4 each time? no matter what seed? How shitty an RNG can you make -_-), and wanted to go to bed Very Happy

. Anywho, I figure I'll add some niftier protection and fix that noargument-crash sillieness later.

What I wanted to do was make the important functions reside in dynamically allocated memory, but I was a little scared of how hard that would be (and the lack of resources online). So instead, I made it have several identical functions, made function pointer arrays, and made it pick one semi-randomly each time (its actually seconds modulo 5 -_-, due to issues with rand()). So, if you break in one of those functions, and rerun, it probably won't hit your break. Once you realize that and break on all of them, you still gotta do the math to reverse it. Tomarrow (instead of doing Calculus homework) I think I'll actually try to solve it myself Very Happy

.

If you would be so generous, it would be great if you could show me how to have a function residing in dynamically allocated memory.

Cheers,
~nog_lorp