Forensics – WhitePages

WhitePages - 250pt

Challenge

I stopped using YellowPages and moved onto WhitePages... but the page they gave me is all blank!

Solution

If we cat whitepages.txt we can see that apparently it's all spaces so it appears blank.
But if we see the xdump of it we can see a common pattern.

whitepages_hexdump_pattern.png

We have in fact sequences of 0xE28083E28083 and spaces.

We can read the file with python (python 2.7 is used here):

with open('./whitepages.txt') as infile:
    textraw=[line for line in infile]

textraw=textraw[0]
temp=textraw.replace('\xe2\x80\x83','0')
print(temp.replace(' ','1'))

Since we have two sequences, we can convert the space charachter to 1 and the other sequence to 0. It returns as a string composed of 0 and 1. If we put this in any online binary to text converter (i used https://www.rapidtables.com/convert/number/binary-to-ascii.html) we obtain the flag.

picoCTF{not_all_spaces_are_created_equal_4b502c0f9b9c2ab6f03f896e5ae09b28}

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