'; document.writeln(my_chunk); } } // --> --> Double Playfair Crypto Contest - Info page
Crypto Challenge : Double Playfair Cipher

Summary, links, news ...

last modified : 10/12/99
New : threads updated (finally :))


The wind was a torrent of darkness among the gusty trees. 

The moon was a ghostly galleon tossed upon cloudy seas. The road was a ribbon of moonlight over the purple moor, And the highwayman came riding-- Riding--riding-- The highwayman came riding, up to the old inn-door.


A New Challenge


The background story : An unknown contributor gave us a Double Playfair Code to crack.
This time : no time limit.

The Task :
If you don't mind an outsider joining the fun, here is a code for you to crack. (And I thought you all just coded cracks =)

Same basic rules as Nova. Your secret agent is sending an encrypted message using Double Playfair system. They used "STOP" as a break and "MESSAGE ENDS" at the end. The most recent playfair square keywords include BLUE DIAMONDS, HARD LIKE ROCK, OF QUARTZ, CRYSTAL PALACE.

K G R J Q  W V Q E P  X E D Q R  C A G K T  Q M N D N  H Q V E Y  L N C L Z  U M L W G
X M S P U  J A T U P  D T Y S R  C Z S C F  A G N N M  V W M I J  X O R C K  X M G D P
O Z W Y X  K Z X W Z  A G W F W  C W B N J  E H Y G O  F K X Z K  O I W W G  O X P U K
H B X D O  H A L W M  G N U E U  C A X F T  C F O O N  G W M M T  F H W K N  I M V W V 
C X F R P  K V Z Z F  D Z X L D  L U C R G  Y N W W V  H K Z J Z  M N K C K  N C F X X 
X P J Q C  N M L L X  D N V J U  I E H K X  A T I V S  G D M B N  R C R S B  N P J H K
P J U Y K  L D S W X  K X A N H  M Y H W B  J M H E W  M Z A I S  Z M N D R  R Z A A G 
X N Z A N  J O P M V  S G O I R  C K T M M  F Z X O S  P R C N W  D N G N P  D J K H A
Z U W V P  I K Z A S  W V S Q W  K D P F G  W W B W Y  G R I H M  N G R R C  F X R U C 
B O Z P M  B H C N V  V N J B Z  D S M Y C  W T O Q G  G M O E C  D Q N H R  Z Z F H U 
S P M B R  R W Z O N  E G T B G  L X R W K  Z N D H P  Q X L M Z  R R O N K  X R N R C 
F T H B R  C W O C Z  I M L C V  N O Z W Y  R G Z A R  C E O T I  P K D V F  G M F W G 
W W G G C  F J Y N L  B P H W W  K Z S E H  M B L K G  G G G M V  X B W D N  W W M U Y 



Additional information, from our (no longer unknown) friend, PART 1 :

I am not +HIM though I am flattered! You did some good work on the other thread but I can see that
Department X must pass on the intelligence they have gathered (stingy bastards).

The secret agent's girlfriend likes blue diamonds. Strongly suspect it is the keyword for the
second matrix, but he never starts a matrix in the top left corner.


Additional information, from our (no longer unknown) friend, PART 2 :

           ---A-     --C--
           -----     -----
           ---D-     --B--
           -----     ----- 
           -----     -----


      :Well, in our actual double playfair THE LAST STEP IS MISSING ! (Would call this 1+1/2 playfair)

      Considering the NOVA contest's second keyword wasn't even among the possibilities I should call that Double PlayUNFair.

      :To say it again : the only difference to the normal playfair is that you have TWO squares and you get your cipher-text with
      taking the first cipher-letter from square one and the second from square two ! (AB --> CD NOT --> EF). Did I talk clearly - If not
      : please ask again.
      Nevertheless, dear cipher-friend : you say 'making the task easier' - correct, it's a lot easier now, but you should have mentioned
      this at the start of the show ! (else it is twice as hard) - we learn, you learn :)

      You are perhaps correct. As I wrote in my email, I was trying to split the difference between too easy and too hard. 
      To be honest though, I don't think anyone else picked up on it as they, at least publicly, were trying to match UY to either DS or
      SX.
      But the two keywords ARE from the choices given. If you don't feel that my mix of knowns and unknowns is fair then I am
      entirely to blame. 

      --a---a- 


Hints and help, Part One


1. The NOVA Double-Playfair :
Maybe this helps to understand how the Double Playfair works, take it as a training :
(better make a print with note-pad)
Original message : 

T O S T R I K E G R O U P W O 
T A N S T O P Y O U R C O N T
 
A C T I S P R O P R I E T O R 
O F N E W S S T A N D A T B U

X L E I G H A N D C H U D W O 
R T H S T O P P R E P A R E T 

O E X E C U T E P L A N W A L 
K U E R E O N S I X D E C E M  

B E R S T O P N O F U R T H E 
R W I R E L E S S C O N T A C 

T M E S S A 
G E E N D S 

 
Try to get the code : 

T I P P O Y N O Y B Y A K L P
Y N K Q T E S I O O R K S S P

Z D A S P M M P N P Y I T Q B
C O Y L O X N P X T C T Y Y O

Z B G P S Z C X C Q L I C D P
R I M L E K T R R G E K R M P

R B X Y Q M A T F M X Y L Q I
T N W W G D Y G V F E S L N I

G W Q G E N D N O D M P T X K
I R I F V G N I B T D T Y N B

U E W P P S
X M P K W T


with these squares : 

C S B L U               B R I G H
H W F M V               T O N C K
E O G N X               A D E F L 
A R I Q Y               M P Q S U
P D K T Z               V W X Y Z
 



The Threads

Additional service : complete threads as .html-files
ZERO : TheBoard (will only get updated at the end !)
ONE : THREAD : If you want a Double Playfair challenge...
TWO : THREAD : some news, Part 1
THREE : THREAD : some news, Part 2
FOUR : THREAD : just a thought
FIVE : THREAD : Very important


The Double Playfair Cipher : Information links

http://www.pbs.org/wgbh/nova/decoding/doubplayfair.html ~
http://www.io.com/~ritter/LEARNING.HTM anagramming
http://www.io.com/~ritter/ARTS/DYNTRAN2.HTM ~
http://www.geocities.com/SiliconValley/Haven/7174/encsctc.html ~
http://www.metronet.com/~mweston/cryptography.html ~


Page started by The Seeker
Page created: 06/12/1999


choose your way out:

redFravia's (frozen) homepage redThe Seeker's homepage redThe javascript workshop redWhat's new