Tag: crypto

Leet More 2010 SHAdow dROP writeup

Category: reverse Generate a license! shadowdrop.exe Lets start with examining the binary. It installs a SEH handler with “bad guy” message, pushes some binary trash on the stack, opens “license.key“, and for each 5 bytes in reads from license, it calculates their SHA-1 and xors another 20 bytes on stack with hash binary. After xoring …

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Leet More 2010 Strange Cipher writeup

Decrypt this “UPDYUFFRPY\TDDSUITF\R\FARTTITYGPPF\/YSGDFYAAO:DF/TA\IAGR:A//DR/T”. ctf.ifmo.ru:5555 If we connect to the service and try to encrypt \x00, \x01, \x02, \x03, \x04, we can notice that only first two bytes and the last one change: [ GDOPU/SIIR\TDPAFYGDA/:S/EIT\\FS/OA:PRYS/DOIOTIS/GUPPYPS/GIGPUSS\ ] [ GFOPU/SIIR\TDPAFYGDA/:S/EIT\\FS/OA:PRYS/DOIOTIS/GUPPYPS/GIGPUSSE ] [ GGOPU/SIIR\TDPAFYGDA/:S/EIT\\FS/OA:PRYS/DOIOTIS/GUPPYPS/GIGPUSSR ] [ ::OPU/SIIR\TDPAFYGDA/:S/EIT\\FS/OA:PRYS/DOIOTIS/GUPPYPS/GIGPUSST ] There are 16 different chars, so a good idea is to …

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