Wednesday 5 March 2014

Defkthon-2014 Reversing-100

This is my first successful hunting in .NET applications.
This CTF was peculiar and tougher too.Firstly wanted to mention 2 things : there were no admins in IRC,there were no description about challenges.

Lets Get back to work now :-)

Link : https://app.box.com/s/kqnh9l7hyj1hfx4bbiot
File description :
So it is clear that it is a .NET application.
Tools I used -> Jetbrains Dotpeek,You can use Reflector also.
After decompiling and opening Defkthon.cs this is what i found :-)




I looked at the string to which num4 is assigned "B0wB4me4iamr00t" , num3 is 0.
scrolling down i got a hint which was ,

So was easy isn't it.yes the string above is what has to be encrypted using sha1 and later md5'ed.
md5(sha1(B0wB4me4iamr00t)) == md5(9df54a6411ed678cdc925b26794052a882830c25) == 58b4d49e5489be09fc409e4c0b5e66ad

FLAG : 58b4d49e5489be09fc409e4c0b5e66ad

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enter valid comments.Suggestions are most welcome and would be interested in correcting my mistakes.