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[KeygenMe] Fun KeygenMe #2


Office Jesus

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Office Jesus

Hello, everyone!I want to present the next entry in my "Fun" series. This time it's a bit of crypto!Features of this keygenme:

  • Coded (poorly) in MASM
  • Not packed
  • Not for beginners?
  • Difficulty: 2-3/10

I hope you guys solve this and post tutorials (text, flash, anything) in this thread! As always, I fully expect ChOoKi to solve this within five minutes of downloading. I also expect him to half-ass his way through a tutorial and then not post it. :prop:Good luck, everyone! I look forward to your solutions!

 

If you find any bugs, please report them so I can fix them.Cheers,
Office Jesus

 

fkgm2.zip

 

Solutions

Ragdog

DimitarSerg

ChOoKi

Edited by Office Jesus
  • Like 4
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Has it been five minutes yet? :)


 


@Office Jesus: Will pm my solution later to allow other members to enjoy it too :peace:


Edited by ChOoKi
  • Like 2
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What the...? I haven't even opened my eyes :black_eye:


 


Oh well, I guess this is expected when members here are starved for a good kgm and for a long time :D


  • Like 1
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it was easy (some logic, xor, sha, rsa)


**DS** OJ15-37AFB60160FAD50C821C287CB08C7A42


Nice Modulus :)


 


Office Jesus / iNFECTiON


You don't know but you were one of my teachers in keygenning :) when I started my way in RE... in 2010 I learned your tuts with interest (An Exercise in RSA Reversal (RSA128 + MD5), Simple.MD5.kg-OJ(Perfect Uninstaller) and after that I keygenned a lot of commercial software and at this moment RE is my major job in my life.


 


I want say Thanks for your work !


Edited by DimitarSerg
  • Like 3
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DUDE i didnt spoiled out anything otherwise i would have posted a working keygen be faster next time :prop:

 

I dont mean you, I mean the OP.

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am i blind or what?
i see the sha1 vectors ( when initialized and used) , the RSA Public Key but i can't seem to find where it (the RSA Public Key) is been used for the Encryption Process.
:scratch:

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Maybe this will help (Warning: SPOILER!!!)


0040170A  |.  FF75 F0       PUSH DWORD PTR SS:[EBP-10]  ; address to hold RSA public key bignum
0040170D  |.  68 0FCE4000   PUSH 0040CE0F               ; RSA public key string = "10001"
00401712  |.  E8 292A0000   CALL 00404140               ; RSA public key string to bignum call
00401717  |.  FF75 EC       PUSH DWORD PTR SS:[EBP-14]  ; address to hold ModExp result
0040171A  |.  FF75 F4       PUSH DWORD PTR SS:[EBP-0C]  ; bignum1 address = You'll have to find out
0040171D  |.  FF75 F0       PUSH DWORD PTR SS:[EBP-10]  ; bignum2 address = RSA public key bignum
00401720  |.  FF75 FC       PUSH DWORD PTR SS:[EBP-4]   ; bignum3 address = You'll have to find out
00401723  |.  E8 58380000   CALL 00404F80               ; bignum ModExp call
00401728  |.  FF75 EC       PUSH DWORD PTR SS:[EBP-14]  ; ModExp result address
0040172B  |.  FF75 F8       PUSH DWORD PTR SS:[EBP-8]   ; address for ???
0040172E  |.  E8 7D290000   CALL 004040B0               ; bignum compare call = ModExp result <> address for ???

 


p.s: Making a tutorial on this kgm already and it will be posted here as soon as it's finished :)


 


Cheers


Edited by ChOoKi
  • Like 3
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As a note, the package (above) was updated as soon as I detected a silly little bug in "Kg.exe". I think I'm gettng old for this stuff, time will tell :)


  • Like 1
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@kao: I think I was low on sugar earlier (not enough beer) :)


In the last few years there has been a tremendous decline in number of kgms posted here, so chances are very slim at finding "harder targets", mind you that making a tutorial on one of them is futile to most beginners.


Edited by ChOoKi
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this was far to difficult for me, but the solution from ChOoKi is simple awesome :)

thanks for the tutorial dude.

and thanks to Office Jesus for the keygenme.

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@kao: I think I was low on sugar earlier (not enough beer) :)

In the last few years there has been a tremendous decline in number of kgms posted here, so chances are very slim at finding "harder targets", mind you that making a tutorial on one of them is futile to most beginners.

 

It's not the problem... If you want more hard - look at commercial software... There are a lot of different interesting algorithmes and sometimes they are very complex and difficult with custom crypro, some hidden checks and tricks, interesting key structures  and very rarely self-made virtual machines, etc. :)

Edited by DimitarSerg
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It's not the problem... If you want more hard - look at commercial software... There are a lot of different interesting algorithmes and sometimes they are very complex and difficult with custom crypro, some hidden checks and tricks, interesting key structures  and very rarely self-made virtual machines, etc. :)

 

Yeah I disagree, it is allways the same and eventually gets excessively boring, saving one or two exceptions of course. The right crackmes are far more interesting, imo - but ofc this is a personal taste. As a side, note there are other sites for good crackmes, advertising aside I have posted on my blog a few ones I reversed lately - crackmes.de/us also offer a great deal of fun moments.

Edited by xSRTsect
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  • 3 weeks later...

Man I miss the Underground forum with chooki, office jesus and the rest that where very active in the keygen me challenge section. I learn't a lot from all you guys. Now I have forgotten a lot due to not having people like your selfs running keygen me challenges. I would love to get back into it again if I had mentors like the underground forum members..... 


 


Thanks for the tutorial chooki I will definitely have a read of that. 


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