Crack: Find the AlgorithmMethod: Enter the codeTarget: NewbieDifficulty: ModerateRestriction: No patching and please do not redistribute!To save the devil, you need to enter the code to unlock the devil's lifestream before you run out of time!Hint: The code is 8 digit long composed of all numbers!Solution: Post the code (spoiler for everyone else)
Hmmm... these are my findings, I'm not yet finished though... Still a little confused on what is being compared to trigger the fail/success codes. :( Am I close to solving this? :D
mov ecx, 8 ; i'm sure it checks for 8 characters/numbers
LODS BYTE PTR DS:[ESI] ; read chars left to right
push eax ; preserve value of eax
mov eax, edx ; copy to eax
pop eax ; above line useless? We are actually be computing the last value from stack, not edx
add al,18 ; this to this seems
sub al,0C ; useless because
add al,18 ; after the last line
sub al,24 ; the initial value = to the result
mov edx, eax
STOS BYTE PTR ES:[EDI]
cmp ecx, 0 ; check counter
ja @CheckChar ; next character
LEA EAX,DWORD PTR DS:
MOV EDX,DWORD PTR DS:[EAX]
MOV ECX,DWORD PTR DS:[EAX+4]
LEA EAX,DWORD PTR DS:[40407D]
SUB EDX,DWORD PTR DS:[EAX]
SUB ECX,DWORD PTR DS:[EAX+4]
add edx, ecx
add edx, eax
or edx, edx
I haven't started it yet...
Right now, I am too busy studying ASP.NET... it's a job requirement and have to pass a certification exam. Too tedious...
I think I found a crucial part of the code;
004012DF LEA EAX,DWORD PTR DS: ; eax contains the correct number
004012E5 MOV EDX,DWORD PTR DS:[EAX] ; the first 4 digits are copied to edx
004012E7 MOV ECX,DWORD PTR DS:[EAX+4] ; the last 4 digits to ecx
004012EA LEA EAX,DWORD PTR DS:[40407D] ; our number copied to eax
004012F0 SUB EDX,DWORD PTR DS:[EAX] ; first 4 correct and our number subtracted, result in edx
004012F2 SUB ECX,DWORD PTR DS:[EAX+4] ; last 4 digits of correct and our number subtracted, result in ecx
004012F5 ADD EDX,ECX ; add the result of edx and ecx
004012F7 OR EDX,EDX ; is it zero? (0 means we've got a boy!)
Then nothing happens if it is not zero...
IF THAT IS THE CASE, THEN THE CORRECT NUMBER IS...
We'll be waiting for your next challenge!!! More! More! More! Thanks!
Nice!This is a cue that somebody has to create a new challenge
Thanks chris! I learned a lot of tricks from this challenge, more please! ;)
I'm working on one, but this will take a while. So, why not post yours to further delay mine? Hahaha!
@Modchip - Spoiler!!! hahaha.
Anyways, I'll review modchip's answer and I'll ask some few questions if I have any. :-)