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PGKKW XIMAF TNEGA NFYGZ TMUIV (Posted on 2003-12-05) Difficulty: 5 of 5
WATAE TXLAL PDIBI MGTBU YBTMM FJBJW KBEIZ SGLZQ CCOCT XMQHM QSLFS
AOBFX QQRCK CJSME XFHLT GYSJN QEQUM FNPIZ ZMCWE PXQOD UIDLO SXLCV
CGIWI UIVYC HLYAE TKYKY RVOVZ FJWAR RCYCN SSJNN ADVZB BMQJQ UVGKC
UCPVN BGRZA EVOMF THBSK OZUYQ QDGUO FUIAT XOWPN QESJM MUHHU XBTMM
NYGYF YFNFH VIATB UOHPD QVJAT AEYLT MQTLE EXBTH MMYCT BDDAX
Determine what this cipher says, and the method of encryption, using the following hints:
  • It is not a simple substitution cipher.
  • Both the original plain text message and the encrypted message contain 270 characters (maybe with meaningless filler characters at the end).
  • Only one rather simple method of encryption has been used.
  • The encryption method is fairly robust. In other words, an error (while encrypting or decrypting) does not scramble the entire remaining message. Some very complicated ciphers have this problem.
  • In the encrypted text, M and T appear most often, and R appears least often (I do not think these facts help at all).
  • Both the original plain text and the encrypted message read from left to right.
  • You might be able to guess the full text after determining only the first three words.

  Submitted by DJ    
Rating: 4.1111 (9 votes)
Solution: (Hide)
The first thing you should notice is that the letters are in groups of five. So, one would assume that the spaces (and probably punctuation) have been removed, and meaningless spaces have been added after every fifth letter, for readability. This makes any cipher harder to decrypt.

This text is encrypted by adding each 'real' letter to the encrypted letter before it, modulo 26 with A=0 and Z=25.
 0  1  2  3  4  5  6  7  8  9 10 11 12
 A  B  C  D  E  F  G  H  I  J  K  L  M

13 14 15 16 17 18 19 20 21 22 23 24 25
 N  O  P  Q  R  S  T  U  V  W  X  Y  Z
As an exmple, let's encode the phrase "CODE WORD." The numeric representation of this word is:
 C  O  D  E  W  O  R  D
 2 14  3  4 22 14 17  3
The first letter, C, will remain since there are no letters before it:
 C  O  D  E  W  O  R  D
 2 14  3  4 22 14 17  3
 2
Each number is determined by adding the number to the encrypted value preceding it:
 C  O  D  E  W  O  R  D
 2 14  3  4 22 14 17  3
 2 16 19 23 45
Whenever the value is above 25, subtract 26 to get the new value (hence the mod scale):
 C  O  D  E  W  O  R  D
 2 14  3  4 22 14 17  3
 2 16 19 23 19
Thus, the entire encryption (with the resulting letters):
 C  O  D  E  W  O  R  D
 2 14  3  4 22 14 17  3
 2 16 19 23 19  7 24  1
 C  Q  T  X  T  H  Y  B
To decode this, we simply need to subtract instead of add. Each number (except the first, which is the same) is found by subtracting the previous number in the encrypted message:
 C  Q  T  X  T  H  Y  B
 2 16 19 23 19  7 24  1
 2 14  3  4 -4
If the result is negative, add 26 (making -4 become 22). So, the unencrypted code is (of course):
 C  Q  T  X  T  H  Y  B
 2 16 19 23 19  7 24  1
 2 14  3  4 22 14 17  3
 C  O  D  E  W  O  R  D
Anyway, after that lengthy introduction, let's tackle the original problem.
The first letter, W, remains the same, as in our model. Let's look at just the first few groups of letters to start:
 W  A  T  A  E  T  X  L  A  L  P  D  I  B  I
22  0 19  0  4 19 23 11  0 11 15  3  8  1  8
22  4 19  7  4 15  4 14 15 11  4 14  5 19  7
 W  E  T  H  E  P  E  O  P  L  E  O  F  T  H
The first three words (as suggested by the clue) are pretty much a dead giveaway to the preamble to the constitution. The entire solution follows:
  W  A  T  A  E  T  X  L  A  L  P  D  I  B  I
 22  0 19  0  4 19 23 11  0 11 15  3  8  1  8
 22  4 19  7  4 15  4 14 15 11  4 14  5 19  7
  W  E  T  H  E  P  E  O  P  L  E  O  F  T  H

  M  G  T  B  U  Y  B  T  M  M  F  J  B  J  W
 12  6 19  1 20 24  1 19 12 12  5  9  1  9 22
  4 20 13  8 19  4  3 18 19  0 19  4 18  8 13
  E  U  N  I  T  E  D  S  T  A  T  E  S  I  N

  K  B  E  I  Z  S  G  L  Z  Q  C  C  O  C  T
 10  1  4  8 25 18  6 11 25 16  2  2 14  2 19
 14 17  3  4 17 19 14  5 14 17 12  0 12 14 17
  O  R  D  E  R  T  O  F  O  R  M  A  M  O  R

  X  M  Q  H  M  Q  S  L  F  S  A  O  B  F  X
 23 12 16  7 12 16 18 11  5 18  0 14  1  5 23
  4 15  4 17  5  4  2 19 20 13  8 14 13  4 18
  E  P  E  R  F  E  C  T  U  N  I  O  N  E  S

  Q  Q  R  C  K  C  J  S  M  E  X  F  H  L  T
 16 16 17  2 10  2  9 18 12  4 23  5  7 11 19
 19  0  1 11  8 18  7  9 20 18 19  8  2  4  8
  T  A  B  L  I  S  H  J  U  S  T  I  C  E  I

  G  Y  S  J  N  Q  E  Q  U  M  F  N  P  I  Z
  6 24 18  9 13 16  4 16 20 12  5 13 15  8 25
 13 18 20 17  4  3 14 12  4 18 19  8  2 19 17
  N  S  U  R  E  D  O  M  E  S  T  I  C  T  R

  Z  M  C  W  E  P  X  Q  O  D  U  I  D  L  O
 25 12  2 22  4 15 23 16 14  3 20  8  3 11 14
  0 13 16 20  8 11  8 19 24 15 17 14 21  8  3
  A  N  Q  U  I  L  I  T  Y  P  R  O  V  I  D

  S  X  L  C  V  C  G  I  W  I  U  I  V  Y  C
 18 23 11  2 21  2  6  8 22  8 20  8 21 24  2
  4  5 14 17 19  7  4  2 14 12 12 14 13  3  4
  E  F  O  R  T  H  E  C  O  M  M  O  N  D  E

  H  L  Y  A  E  T  K  Y  K  Y  R  V  O  V  Z
  7 11 24  0  4 19 10 24 10 24 17 21 14 21 25
  5  4 13 18  4 15 17 14 12 14 19  4 19  7  4
  F  E  N  S  E  P  R  O  M  O  T  E  T  H  E

  F  J  W  A  R  R  C  Y  C  N  S  S  J  N  N
  5  9 22  0 17 17  2 24  2 13 18 18  9 13 13
  6  4 13  4 17  0 11 22  4 11  5  0 17  4  0
  G  E  N  E  R  A  L  W  E  L  F  A  R  E  A

  A  D  V  Z  B  B  M  Q  J  Q  U  V  G  K  C
  0  3 21 25  1  1 12 16  9 16 20 21  6 10  2
 13  3 18  4  2 20 17  4 19  7  4  1 11  4 18
  N  D  S  E  C  U  R  E  T  H  E  B  L  E  S

  U  C  P  V  N  B  G  R  Z  A  E  V  O  M  F
 20  2 15 21 13  1  6 17 25  0  4 21 14 12  5
 18  8 13  6 18 14  5 11  8  1  4 17 19 24 19
  S  I  N  G  S  O  F  L  I  B  E  R  T  Y  T

  T  H  B  S  K  O  Z  U  Y  Q  Q  D  G  U  O
 19  7  1 18 10 14 25 20 24 16 16  3  6 20 14
 14 14 20 17 18  4 11 21  4 18  0 13  3 14 20
  O  O  U  R  S  E  L  V  E  S  A  N  D  O  U

  F  U  I  A  T  X  O  W  P  N  Q  E  S  J  M
  5 20  8  0 19 23 14 22 15 13 16  4 18  9 12
 17 15 14 18 19  4 17  8 19 24  3 14 14 17  3
  R  P  O  S  T  E  R  I  T  Y  D  O  O  R  D

  M  U  H  H  U  X  B  T  M  M  N  Y  G  Y  F
 12 20  7  7 20 23  1 19 12 12 13 24  6 24  5
  0  8 13  0 13  3  4 18 19  0  1 11  8 18  7
  A  I  N  A  N  D  E  S  T  A  B  L  I  S  H

  Y  F  N  F  H  V  I  A  T  B  U  O  H  P  D
 24  5 13  5  7 21  8  0 19  1 20 14  7 15  3
 19  7  8 18  2 14 13 18 19  8 19 20 19  8 14
  T  H  I  S  C  O  N  S  T  I  T  U  T  I  O

  Q  V  J  A  T  A  E  Y  L  T  M  Q  T  L  E
 16 21  9  0 19  0  4 24 11 19 12 16 19 11  4
 13  5 14 17 19  7  4 20 13  8 19  4  3 18 19
  N  F  O  R  T  H  E  U  N  I  T  E  D  S  T

  E  X  B  T  H  M  M  Y  C  T  B  D  D  A  X
  4 23  1 19  7 12 12 24  2 19  1  3  3  0 23
  0 19  4 18 14  5  0 12  4 17  8  2  0 23 23
  A  T  E  S  O  F  A  M  E  R  I  C  A  X  X
And with punctuation and everything:

We the people of the United States, in order to form a more perfect union, establish justice, insure domestic tranquility, provide for the common defense, promote the general welfare, and secure the blessings of liberty to ourselves and our posterity, do ordain and establish this Constitution for the United States of America.

Lastly, the title becomes:
  P  G  K  K  W  X  I  M  A  F  T  N  E
 15  6 10 10 22 23  8 12  0  5 19 13  4
 15 17  4  0 12  1 11  4 14  5 14 20 17
  P  R  E  A  M  B  L  E  O  F  O  U  R

  G  A  N  F  Y  G  Z  T  M  U  I  V  
  6  0 13  5 24  6 25 19 12 20  8 21
  2 14 13 18 19  8 19 20 19  8 14 13
  C  O  N  S  T  I  T  U  T  I  O  N
Original puzzle by Jim Loy.

Comments: ( You must be logged in to post comments.)
  Subject Author Date
re(2): the actual decryptionTristan2003-12-10 19:24:34
re(2): the actual decryption -- exceptCharlie2003-12-10 09:02:17
Solutionre: the actual decryptionSilverKnight2003-12-09 20:45:51
Some Thoughtsthe actual decryptionTristan2003-12-09 20:19:57
re(3): SolutionTristan2003-12-08 17:30:38
re(2): SolutionCharlie2003-12-08 15:46:49
re: SolutionPenny2003-12-08 13:46:36
Hints/TipsSolutionDJ2003-12-08 12:12:50
re: Solution?fwaff2003-12-08 06:14:06
re(2): Solution?S2003-12-07 19:04:27
IdeasGamer2003-12-06 12:05:18
re: Some ThoughtsSam2003-12-06 09:29:54
re: Some ThoughtsCharlie2003-12-06 00:44:10
re: Solution?Penny2003-12-05 22:46:57
Some ThoughtsSam2003-12-05 22:36:40
SolutionSolution?Penny2003-12-05 22:24:35
re(2): hmm...Victor Zapana2003-12-05 21:20:44
Some Thoughtsre: hmm...Federico Kereki2003-12-05 20:40:37
Some Thoughtshmm...Tristan2003-12-05 18:25:35
really really stumped...Victor Zapana2003-12-05 17:28:11
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