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[CrackMe] zxcEncryptor -- Attempt 2

 
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False Prophet
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Joined: 28 May 2006
Posts: 121

PostPosted: Tue Oct 27, 2009 6:36 am    Post subject: [CrackMe] zxcEncryptor -- Attempt 2 Reply with quote

Alright, my very first attempt at making a CrackMe failed 2 or 3 hours later.
Here is my second attempt.
There is no predetermined key.
I've added dummy code, and used a little bit of Assembly.

If you figure it out, please post how you did it.
My last attempt had direct comparison. This shouldn't have that(I hope).

Download: here.

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Last edited by False Prophet on Tue Oct 27, 2009 6:58 am; edited 1 time in total
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Bswap
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Joined: 18 Aug 2009
Posts: 21

PostPosted: Tue Oct 27, 2009 6:53 am    Post subject: re: Reply with quote

Breakpoint @0040758F;

Code:
00407583  |. 030D F8C04000  |ADD ECX,DWORD PTR DS:[40C0F8]
00407589  |. 0315 F8C04000  |ADD EDX,DWORD PTR DS:[40C0F8]
0040758F  |. E8 5C2D0000    |CALL zxcEncyp.0040A2F0


Code:
ECX 003F07E0 ASCII "1234567890" (what I entered)
EDX 003F07EB ASCII "tf08n5vnyofajzucf3cs" (valid computed serial)


Modify the ECX (003F07E0) register so that it's contents are the same as EDX (003F07EB).

Code:
ECX 003F07EB ASCII "tf08n5vnyofajzucf3cs"
EDX 003F07EB ASCII "tf08n5vnyofajzucf3cs"


F9 to continue execution.

"Unlocked!"
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False Prophet
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PostPosted: Tue Oct 27, 2009 6:59 am    Post subject: Reply with quote

Damn, I suck. Shocked
Nice job. + rep for you!

[Edit] I was going to add an encryption rotate code, but decided against it. Maybe I should do that?

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Bswap
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PostPosted: Tue Oct 27, 2009 7:10 am    Post subject: re: Reply with quote

Parts of the program are nice.

Code:
=-)
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False Prophet
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PostPosted: Tue Oct 27, 2009 7:16 am    Post subject: Re: re: Reply with quote

Bswap wrote:
Parts of the program are nice.

Code:
=-)


Thank you Laughing

I think I am slowly strengthening my program.
I hope that I'll be able to make something much more secure with a little bit more practice.

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DoomsDay
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PostPosted: Tue Oct 27, 2009 9:50 am    Post subject: Reply with quote

You should modify the entered password and then compare it against a constant, or, in case of a keygenme, a different item generated from the user-name\id\etc.
An axample would be:
if (rotate1(name) == rotate2(password))...
when the rotate algorithms differ.
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False Prophet
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PostPosted: Tue Oct 27, 2009 8:59 pm    Post subject: Reply with quote

What would the best method be at creating an "uncrackable" crackme?

CRC's?

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&Vage
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PostPosted: Wed Oct 28, 2009 4:31 pm    Post subject: Reply with quote

Nothing is uncrackable, what I do is use the custom hash of my string and compare it to a hashed user inputted string.
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mingyuan
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PostPosted: Mon Sep 12, 2011 2:35 am    Post subject: Reply with quote

&Vage wrote:
Nothing is uncrackable, what I do is use the custom hash of my string and compare it to a hashed user inputted string.


then other people can crack the compare ,such as jnz --> jz ,
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