Thursday, 31 October 2013

EMCDefendersleague2013 week-1 challenge-3 solution

File can be downloaded here :

Challenge 3 :
question : Everybody loves HTML. It’s good looking and all sources available. View the source, find the answer and impress us!

Hint 1:Decode and find the logic.

file name : Contest3.sample.gz

I hope you remember from my last post how to decompress a gzip file 
gzip -d Contest3.sample.gz will give you the file.

doing a file command on extracted file will tell us that its a HTML document.
file Contest3.sample
result : Contest3.sample: HTML document text

so replace Contest3.sample to Contest3.html
opening it in browser gives you this : 

the logic is to do a arithmetic calculation of a number and the result to be zero.meaning 30-10-10-10=0 ,it can be anything it can be 40-20-10-10 also

you would get this :

The flag is : YYgiMLTve8deLtGrlbzC29bAW

There is an other way of solving it, i will just tell you the way you can try it out.
There is a eval function which consists of hex values.changing it to ASCII you would get again a hex value again convert it to ASCII,the same repeat it again.finally after 3 times of this you would get a function.Now xor it.look at the function you get.the logic says to xor it.try it out.I have given a rough idea.try it out as a exercise :-)


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