Rotting Away Writeup

Rotting Away Writeup
by DeathsPirate
$who

Challenge:
WZCFILORUXADGJMPSVYBEHKOQTWZCFILORUXADGJMPSVYBEHKNQTWZCGILORUXADGJMPSVYBEHKNQTWZCFILOQUXADGJMPSVYBEHKNQTWZCFILORUXADGJMQSVYBEHKNQTWZCFILORUXADGJMPSVYBFHKNQTWZCFILOQUXADGJMPSVYBEHKNQTWZCFILORUXADHJMPSVYBEHKNQTWZCFILORUXADGJMPSVYBEHKNQTWZCFILORUXADGJMQSVYBEHKNQTWZCFILORUXADGJMPSWYBEHKNQTWZDFILORUXADGJMPSVYBEHKNQTWZCFILORVXADGJMPSVYBEHKNQTWZCFILOQUXADGJMPSVYBEHKNQTWZCFILORUXADGJMPSVYBFHKNQT


Solution:

Take a look at the string and you'll notice that there are what appear to be repeating sections,
let's split it up so it makes that easier to see:

WZCFILORUXADGJMPSVYBEHKOQT
WZCFILORUXADGJMPSVYBEHKNQT
WZCGILORUXADGJMPSVYBEHKNQT
WZCFILOQUXADGJMPSVYBEHKNQT
WZCFILORUXADGJMQSVYBEHKNQT
WZCFILORUXADGJMPSVYBFHKNQT
WZCFILOQUXADGJMPSVYBEHKNQT
WZCFILORUXADHJMPSVYBEHKNQT
WZCFILORUXADGJMPSVYBEHKNQT
WZCFILORUXADGJMQSVYBEHKNQT
WZCFILORUXADGJMPSWYBEHKNQT
WZDFILORUXADGJMPSVYBEHKNQT
WZCFILORVXADGJMPSVYBEHKNQT
WZCFILOQUXADGJMPSVYBEHKNQT
WZCFILORUXADGJMPSVYBFHKNQT

It seems that there in certain lines one letter is changed.
It also seems that each line contains 26 chars ... hmm the alphabet has 26 chars.
Let's order each line alphabetically and see what we get:

<code>
#!/usr/local/bin/python2.7

t = [
'WZCFILORUXADGJMPSVYBEHKOQT',
'WZCFILORUXADGJMPSVYBEHKNQT',
'WZCGILORUXADGJMPSVYBEHKNQT',
'WZCFILOQUXADGJMPSVYBEHKNQT',
'WZCFILORUXADGJMQSVYBEHKNQT',
'WZCFILORUXADGJMPSVYBFHKNQT',
'WZCFILOQUXADGJMPSVYBEHKNQT',
'WZCFILORUXADHJMPSVYBEHKNQT',
'WZCFILORUXADGJMPSVYBEHKNQT',
'WZCFILORUXADGJMQSVYBEHKNQT',
'WZCFILORUXADGJMPSWYBEHKNQT',
'WZDFILORUXADGJMPSVYBEHKNQT',
'WZCFILORVXADGJMPSVYBEHKNQT',
'WZCFILOQUXADGJMPSVYBEHKNQT',
'WZCFILORUXADGJMPSVYBFHKNQT']

for l in t:
  print ''.join(sorted(l))

</code>

Outputs:

ABCDEFGHIJKLMOOPQRSTUVWXYZ
ABCDEFGHIJKLMNOPQRSTUVWXYZ
ABCDEGGHIJKLMNOPQRSTUVWXYZ
ABCDEFGHIJKLMNOPQQSTUVWXYZ
ABCDEFGHIJKLMNOQQRSTUVWXYZ
ABCDFFGHIJKLMNOPQRSTUVWXYZ
ABCDEFGHIJKLMNOPQQSTUVWXYZ
ABCDEFHHIJKLMNOPQRSTUVWXYZ
ABCDEFGHIJKLMNOPQRSTUVWXYZ
ABCDEFGHIJKLMNOQQRSTUVWXYZ
ABCDEFGHIJKLMNOPQRSTUWWXYZ
ABDDEFGHIJKLMNOPQRSTUVWXYZ
ABCDEFGHIJKLMNOPQRSTVVWXYZ
ABCDEFGHIJKLMNOPQQSTUVWXYZ
ABCDFFGHIJKLMNOPQRSTUVWXYZ

Ok this looks like we are on the right track with this.
Some lines have repeated letters and some don't.
Let's pull out repeated letters and assume that no repeats is a space:

O GQQFWH QWDVQF

Looks like some ROT going on ... let's rot it
Using ROT13 didn't give anything meaningful so ran it through all ROT combinations,
ROT12 gave us this:

A SCCRIT CIPHCR

Guessed that this would probably be A SECRET CIPHER ... popped it in to the flag submission and completed challenge.