See Part I | See Part II | See Part IV

Finally, you've gained access to his files... but the filenames are all encrypted! Oh, no!

file directory

You only have one chance to open the files! Which one should you open and why? (Hint: the file sizes have nothing to do with your answer!)

  • $\begingroup$ Do the specifics of the characters matter, or are they just symbols? For example, does it matter that "è" is "è" and not "ð", or are they just arbitrarily chosen glyphs? In the former case, you might want to put the textual version in the puzzle, too. $\endgroup$
    – Bobson
    May 8, 2019 at 19:01
  • $\begingroup$ @Bobson That is a question that I will answer as a hint if enough time has passed... $\endgroup$ May 8, 2019 at 20:53

2 Answers 2


This is

the result of doubling the character codes of all the characters in the following names: Wrong, Incorrect, ThisIsIt, NotIt, IsntImportant, Nonexistent, Virus.

So I think you want

the third one.


put ''.join(chr(2*ord(c)) for c in 'Wrong Incorrect ThisIsIt NotIt IsntImportant Nonexistent Virus').replace('@',' ').replace('\x92','_').replace('\x9c','_') into a Python 3 interpreter -- @ is what a space turns into, and characters 92 and 9c are the ones that are being displayed as little boxes.

The main difficulty here was

with transcription -- in several cases it wasn't clear whether we're looking at a capital or a lowercase letter, for instance. I actually noticed some time ago that a lot of the characters seem to have even character codes, but some of them appeared not to because I had guessed wrongly at what they were :-).

  • $\begingroup$ I thought it might be something like this, but I lost interest in trying to transcribe it to play around with it. I can confirm that I get the same results doing this transform in C#, so I think this is the right answer. $\endgroup$
    – Bobson
    May 9, 2019 at 14:31
  • $\begingroup$ I used Python to encode it! :) $\endgroup$ May 9, 2019 at 14:32
  • $\begingroup$ Well, of course :-). $\endgroup$
    – Gareth McCaughan
    May 9, 2019 at 15:29
  • $\begingroup$ Thanks for the nice juicy bounty :-). $\endgroup$
    – Gareth McCaughan
    May 9, 2019 at 17:38
  • $\begingroup$ @GarethMcCaughan No problem! $\endgroup$ May 10, 2019 at 17:08

The answer is:

According to my understanding filename need to start with certain characters only. It won't start with with special characters and spaces. So I will open the last file in the above image which is 83 MB.

  • $\begingroup$ Sorry, not correct, and you’re not really on the right track, . $\endgroup$ May 9, 2019 at 10:41
  • $\begingroup$ Don’t assume that the filenames are that of a regular computer. $\endgroup$ May 9, 2019 at 10:45

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