``````-- CIPHERTEXT --
AEBRVHWWMQHURVWFFIKVYFUCDG
To Decrypt this Message, you will need to learn how a US President encrypted messages while in Paris France.

The PSK sequence you need to know is:
5,24,4,20,23,2,11,22,19,15,10,18,16,1,14,3,25,9,6,12,26,7,13,17,21,8
``````

## Solve

Began with the obvious of throwing the ciphertext into quipquip for easy pickings, no dice. Actually opened up the pdf to see a 2x2 grid of letters and then a circle at the bottom the size of a paper towel roll. This immediately sparked the memory of the Da Vinci Code cryptex. I began doing some awkward transformations of shifting each letter in the cipher text a number in the PSK: ``` A » 5 E » 24 B » 4 R » 20 … ect

``````
Realizing this was a terrible idea, went back to the PDF to realize that there are numbers at the top of the 2x2 grid. It then became obvious that the PSK given is the order of the tumblers needed to solve the ciphertext.

The solution script does the following:

* Extracts each individual tumbler
* Arranges the tumblers in order based on the PSK
* Rotates each tumbler to match the ciphertext
* Prints every resulting line

Upon execution, we are given the following result:

``````

AEBRVHWWMQHURVWFFIKVYFUCDG XCDSNUMEXWPMMLNGHMNXOYGVET KXVDCRBLWOURKYSBVPDJAMFBUW MJZZIICYVMDNHTYMZXUDIIZFHK BQNMFJJJSUJFYFPQKYOYTNWJKB SBFTPZVDUHWLGUJYQEQWEWIONA PFXQTQPXBCFQEWLSTSYOQSSRVL HTTPHCSAINTCONORGJEFFERSON <— Looks like a web page IVKHZKAUGJNIIMFPMTRBDHTIPV TMQUXWZOEDGBXCGUWQPEBBMNAD OYUWSYENFLIJNJKTCBZAPJAZRE GAEXRPRKHKMHQDXDRAJTSOXXQX WKPKOXDCDVVPDKCOPDLRCPPYSP RLHGWVLFAIEVJZILSZWPXVHMXI FHSVQMKQKYOWVPQAJOTCVQDPBS LZYOAEOVNRQYBBDZDRXNRKBAFM UDLAKSURJPADLSBXLUBQLZCUYF YUICLLGSPFKGTGUNBGSUJAVQGO NPMIGTYTOTBKFETKYVILUUEWMQ EIOEUNNMZGZZWRMVAKCINDYLCH DGAJJDTHLSXSAXVJOFFZMTKHIY JOGLEGQIRAYOCAECNHHSZGODJJ ZNWFBBFPCXCTSQZHECVGKCQTLZ VSRBMAHGQZSAZIHEILAHWRJGWC CWJYDOIZYBLEPHAWUNMMHXLETR QRCNYFXBTERXUORIXWGKGLNKZU

``````
Checking out the website:

``````

PROVE YOU SOLVED IT! DM TWEET @SAINTCON: The Ciphertext three positions below the Plaintext If you hate Twitter, an email to tj@saintcon.org will work too.

SOLVED BY: NOBODY YET

``````
I don't think I was the first, but it was a great challenge nonetheless! Thanks to @saintcon for the pre-challenge and looking forward to more puzzles in the future.

## Final solution

```python

from collections import deque

ciphertext = 'AEBRVHWWMQHURVWFFIKVYFUCDG'
cipher = '''
R C X G O R U Q P T U V X L Z N Q S P V P I T M K E
X K N W G P D H X N G X P O B Q W O O O A P H Y Q Q
A W K R W Z T Y Y G Y J H F E D L T Z A R G Z A T F
Q Y V J R J G J E I N D D G Q J H A L C Q Z X K G D
I P J C F L C Z S M T Y B K W V D E R I S B S L M B
H X C B L W R C J V Q W C X O B T X C E X W R H W P
O V H D U T X R T E F O V C M L G U Q J B E O Z C S
V M E V Y X L U Q O H F E I U T E M Y L F L W D R C
L E W Z N B F G B Q I B Y Q H F K R T F Y Y Q U P X
Y S I N E S Y T A A X E K D C W C N M B G J A P S V
T L F F D I M W D K W A O B N A V F X Y M D K I J R
F T G X J C I K Z B M T Q U J C B L W N C X L G D L
U N B T Z F N B O Z B R J T D S F Q V R I A G O L J
W D M K V H W A R X C P L M L Z J C S S J U U N B U
N G Q Q C V S L U Y J C N V K P O I U D L O J S Y N
M B Y U Q A E N G C V N U E V U R B B Z W N E W A M
C A S E A M H V V S P Q G Z I R S J I M T K B R O Z
J O R P X G B D K L S U F H Y M I H G T Z C M E N K
D F P H K K J E F R A L Z A R K N P E Q D F D C E W
K H U S M N O X H H Z I W R P H Z V F P E Q Y X I H
Z U T Y B D P P C P E Z I W F Y X W H H U V V J U G
P R D L S U V I L U R S S N T G Y Y D U H R N Q X Y
B I O I P O Q S N D D G R S G E M D A W K S C B F O
S J L M H Q K M W J L H T Y S O P G K X N T I F H A
G Z A O I Y Z F I W K M M P A I A K N K V M F T V I
E Q Z A T E A O M F O K A J X X U Z J G O H P V Z T
'''

# Convert grid to 26 individual tumblers
cipher = zip(*[x.split() for x in cipher.splitlines()[1:]])

tumblers = []
final = []
psk = [5,24,4,20,23,2,11,22,19,15,10,18,16,1,14,3,25,9,6,12,26,7,13,17,21,8]

# Create cryptex
for index in psk:
tumblers.append(cipher[index-1])

# Rotate tumblers to read ciphertext
for index,tumbler in enumerate(tumblers):
tumbler = deque(tumbler)
while tumbler != ciphertext[index]:
tumbler.rotate(1)

final.append(list(tumbler))

# Flip 2D array to read everyline
"""
a b
c d
|
v
a c
b d
"""
final = zip(*final)

# Print all
for f in final:
print ''.join(f)
``````
For relevant code for this writeup:
``git clone https://github.com/ctfhacker/ctf-writeups``