home
***
CD-ROM
|
disk
|
FTP
|
other
***
search
/
Reverse Code Engineering RCE CD +sandman 2000
/
ReverseCodeEngineeringRceCdsandman2000.iso
/
RCE
/
E_bliss
/
siflying_vizion_crackme.txt
< prev
next >
Wrap
Text File
|
2000-05-25
|
3KB
|
66 lines
Target : Crackme 1.02 by Vizion/Mexelite (on Eternal Bliss site :
http://www.crackmes.cjb.net )
...a little tut by SiFLyiNG...
In this little tutorial (if we can call that a tutorial, i'll only explain
brievly the method i used to find a correct serial for this crackme.
Let's go :
Name: what you want
Serial : 12345678
advise : note your personal code, it could be useful for the following
Bpx hmemcpy in sice
1. At the beginning of the check, it compares the len of the entered
code to Eh (h means hexadecimal, so Eh = 14 in decimal base ). So it means that the serial must look like : XXXXXXXXXXXXXX (14 times)
2. then it compares the fourth char of the serial with 2Dh, so it compares
with "-". So the serial must be XXX-XXXXXXXXXXX
3.there is a first comparation :
the asm code is :
MOV ECX, EAX ; first part XXX of the entered serial
(in my case 123)
MOV EAX, [00430700] ; personal code (in my case 1078268636
MOV EBX, FF ; move FFh in EBX
CDQ
IDIV EBX ; EAX = EAX/EBX = EAX/FFh
the rest from the division is stored
in EDX ; in my case EDX = 74h
then the verification : XOR ECX, EDX
JNZ bad cracker
So, it means that ECX should be equal to EDX so that the prog won't jump.
ECX XOR EDX = 0 means that ECX = EDX so ECX must be 74h = 116 not to jump
to the bad cracker code
So the first part of the serial is : 116
There I know that my serial must look like : 116-YYYYYYYYYY (10 times)
4.Then there is some loops which calculate the second part of the code from
the entered name and the personnal code. Then there is - I don't show any
adress so you have got some work to make :
XOR ESI, EAX ; EAX = entered second part of code and ESI = real second
part of code
JNZ bad cracker ; the result must be ESI = 0 not to jump so EAX(our code)
must be equal to ESI(good code)
so you can get the valid second part of the code. But you should first look
at the calculation code and try to make a keygen :)
I press the test button and look at the status bar :
"Correct serial... it's time for a keymaker..."
Try with your name & personnal code with the same scheme :
you must manage now :)
i haven't time to write a real tutor, so mail me if you have questions :
siflying@ifrance.com