Problem
I stopped using YellowPages and moved onto WhitePages... but the page they gave me is all blank!
Hint
None.
Solution
No hints. This challenge would be a pain in the ass for newbies. But yet :v lets move on.
Given a text file (make sure it's a text file first), I've done cat whitepages.txt but no avail.
EMPTY
But one could comeup with an idea. We know that there is some text over here. But we couldn'ot see it. Remember the ASCII table? Each letter we know had a Decimal form, Hexadecimal form. Got an idea? Lets see.
>>>" ".encode("hex")
'e28083e28083e28083e2808320e2808320e28083e28083e28083e28083e2808320e28083e2808320e28083e28083e28083e2808320e28083e2808320e28083202020e28083e28083e28083e28083e280832020e2808320e28083e2808320e280832020e28083e28083e28.........'One could see that its some sort of repeating text. Well, you are partially correct and wrong.
We have the standard space (0x20), and the Unicode EM SPACE (U+2003 / 0xE2 0x80 0x83).
As there are only two types of unicode, let's treat the following as binary.
We can write a script to automate the process :)
from pwn import *
with open("whitepages.txt", "rb") as binary:
ans = bytearray(binary.read())
ans = data.replace(b'\xe2\x80\x83', b'0')
ans = data.replace(b'\x20', b'1')
ans = data.decode("ascii")
print unbits(ans)pwntools is a library specially made for CTF purposes. Have fun installing it :p
If you couldn't, open the file in a text editor and find and replace the \x20 with 1 and \xe2\x80\x83 with 0.
Running the following script gives you the flag :)
Flag
picoCTF{not_all_spaces_are_created_equal_f006c045f6b402ce4bc749dc7a262380}