downloadadrianbn's lincrackme3

Download lincrackme3.tgz, 5 kb

This is the second of the lincrackme's series. The package contains a 32 bit version and a 64 bit one. The 32 bit version should work fine in a 64 bit system anyway, but just in case...

As usual, the goal is to locate and understand the antidebugging techniques, and learn how to disable them. Once that's done, you have to understand the key checking method and get some valid keys (best if you make a keygen for it!!).

You can patch the binary to bypass the antidebugging techniques (however thats not mandatory), but you shouldn't patch to get the right message. Find the correct key algorithm. Brute-forcing the keys is not allowed either.

My own solution, (and maybe some of yours, if you want) will be published here: http://securityetalii.es with the solutions to the rest of the lincrackmes series (lincrackme2 so far).

PS: Give me all the feedback you can, please, about the difficulty level (is it right?) and everything else. You can contact in the comments or by mail at adrianbn[_AT_]gmail [_dOt_]com. Thanks!

Difficulty: 3 - Getting harder
Platform: Unix/linux etc.
Language: C/C++

Published: 01. Nov, 2010
Downloads: 529

Rating

Votes: 6
Crackme is nothing special.

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Solutions

Solution by hasherezade, published 23. nov, 2010; download (580 kb), password: crackmes.de or browse.

hasherezade has rated this crackme as awesome.

Solution by miguel, published 21. dec, 2010; download (5 kb), password: crackmes.de or browse.

miguel has rated this crackme as nothing special.

Solution by jjjjj, published 21. dec, 2010; download (2 kb), password: crackmes.de or browse.

jjjjj has rated this crackme as nothing special.

The submission of solutions is closed.

Discussion and comments

tamaroth
Moderator
15. Nov 2010		Quite fun. Used ida + remote debugging to get to the code, quite fun. Even though you said no bruteforcing is allowed, i used simple brute force to generate completely random serials. i hope that's enough ;-)

Here are few sample serials:
3912-8939-1011-6139
0436-4302-0400-1033
1725-3837-3107-3220

I'm quite bad at writing tutorials, but maybe i'll drop one once i get some willingness into me ;p
adrianbn
Author
17. Nov 2010		Hi tamaroth,

Im glad you enjoyed the crackme. Did you actually got the key from the code or made a bf program who generates keys and tests them against the crackme? The second one is like cheating! :P

The algo is quite open, in the meaning that there are lots of valid keys, so a bf attempt will likely succeed.

Put some willingness and be the first to submit a solution ;)
tamaroth
Moderator
17. Nov 2010		I'll drop you my keygenerator (it's written in C, all by myself), therefore it's a keygen but it uses some form of brute force (generates random numbers and then check then against the checks that are made inside crackme). See pm with the link to the keygen :)
adrianbn
Author
17. Nov 2010		Tamaroth, that's exactly the kind of solution I was looking for. I first understood that you just generated random numbers and feed the crackme with them to see if they fit. That was obviously not allowed.

However your keygen demonstrates that you've bypassed all the protections, understood the code and code somthing similar in C to find the keys. Very nice job! :)
hasherezade
17. Nov 2010		i solved it too... very pleasant crackme, thank You!
hasherezade
17. Nov 2010		some other sample keys:
5567-5545-5500-5600
4555-9998-7766-1000
^^
I will submit my solution as soon as i will get some time to describe it nicely.
adrianbn
Author
18. Nov 2010		Hi hasherezade,

Good you find the crackme pleasant :) Go for it and post a solution!
miguel
23. Nov 2010		The key algo is funny.
The antidebugging protections are well known by reversers.
My solution is waiting the moderators review since nov, 12th
they may be really busy. ;-)
adrianbn
Author
26. Nov 2010		Finally hasherezade's solution went through. Good job dude! It's very good, both technically and written/explained. I promise I'll publish next crackme (harder ;) soon, Im quite busy at the moment, but december should be a good month to program a little.

Hope there are more solutions on the way (thanks miguel). I love reading how each person solves it in different ways :)
acez
06. Nov 2012		very good crackme, i will post my solution soon
4148-2898-8124-1114
tvk6843
08. Dec 2014		Just for fun :-) The keygen should starts from the sums of the numbers

the key is: 0049-0005-0004-1310
the key is: 0049-0005-0004-1400
the key is: 0049-0005-0004-2003
the key is: 0049-0005-0004-2012
the key is: 0049-0005-0004-2021
the key is: 0049-0005-0004-2030
the key is: 0049-0005-0004-2102
the key is: 0049-0005-0004-2111
the key is: 0049-0005-0004-2120
the key is: 0049-0005-0004-2201
the key is: 0049-0005-0004-2210
the key is: 0049-0005-0004-2300
the key is: 0049-0005-0004-3002
the key is: 0049-0005-0004-3011
the key is: 0049-0005-0004-3020
the key is: 0049-0005-0004-3101
the key is: 0049-0005-0004-3110
the key is: 0049-0005-0004-3200
the key is: 0049-0005-0004-4001
the key is: 0049-0005-0004-4010
the key is: 0049-0005-0004-4100
the key is: 0049-0005-0004-5000
blankwall
24. Apr, 20:41		http://paste.ubuntu.com/16035640/

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