MONOME-DINOME

TEN STEP SOLUTION SEQUENCE

                                                                                                                  LIONEL

  1. Perform a digit frequency count.
  2. All consecutive (double) ciphertext digits are assigned to the top of the Monome-Dinome (MD) key block as singles.
  3. Side (row) digits of the MD block cannot be side by side in the cipher text.
  4. Write text in MD digits.
  5. Perform frequency count of MD digits.
  6. Locate crib.
  7. Fill in known plaintext in MD text.
  8. Post letters to MD key block as you uncover plaintext.
  9. Third row of MD key block is end of alphabet.
  10. Arrange MD key block alphabetically to obtain key word.

This is the ten step solving process to deciphering the Monome-Dinome Cipher. We will apply these steps to the cipher appearing in the JA 2001 issue of The Cryptogram.

E-13.  Monome-Dinome. There are better uses for barrels.    (230)     (falls)      CROTALUS

75385   95124   76782   46437   64164   64638   23519   19295   99004   61949   61645   89345

13578   75383   95264   68835   39638   72518   52517   76164   75351   25244   69263   51638

52945   25152   96064   69315   46460   61517   53643   06090   51598   63847   61536   46194

46186   77646   38275   38599   00495   97829   54649   75131   58514   53967.

STEP ONE – PERFORM A DIGIT FREQUENCY COUNT.

A frequency count of the cipher above will yield the following result:

Digit Freq   Digit Freq
0 9   5 36
1 23   6 35
2 15   7 18
3 23   8 18
4 28   9 25

STEP TWO – ALL CONSECUTIVE (DOUBLE) CIPHERTEXT DIGITS ARE ASSIGNED TO THE TOP OF THE MD BLOCK.

To understand this principle we must discuss the Monome-Dinome (MD) Key Block. It is the block that contains the cipher keyword and differs from our conventional keyword alphabet with two additional lines and only 24 alphabet letters. An MD block may eliminate any two of the alphabet’s infrequent letters. This cipher chooses to eliminate the letters “J” and “X.” The block assigns two of the ten ciphertext digits to the side and eight to the top of the block. It looks like this:

                                  3  4  5  6  7  8  9  0
                                 A  B  C  D  E  F  G  H
                            1    I  K  L  M  N  O  P  Q
                            2    R S  T  U  V W  Y  Z

Steps two and three involve the determination of which digits are placed at the side of the MD block and what digits are placed on top. ALL CONSECUTIVE DIGITS (Double Digits) IN THE CIPHERTEXT ARE ASSIGNED TO THE TOP OF THE MD BLOCK for reasons which will become obvious as we proceed to rewrite the text in Monome-Dinome digits. Look for consecutive digits in the MD ciphertext and assign them to the top of the MD block.

In the above ciphertext, you will find that the digits, 0, 4, 7, 8 and 9 appear beside each other somewhere in the text. We assign these to the top row of the block. We must now look for three more candidates for the top row of the MD block from the five remaining ciphertext digits.

STEP THREE – SIDE (ROW) DIGITS CANNOT BE SIDE BY SIDE IN THE CIPHERTEXT.

When we convert the ciphertext to Monome-Dinome text, the top row digits of the MD blocks are single text digits. The side (row) digits become the first digit of a two digit text number when coupled with the single digits at the top of the MD block. For this reason, side (row) digits cannot be side by side in the ciphertext. If you examine the five remaining digits, 1, 2, 3, 5 and 6, you will find that digits 5 and 6 are the only two digits that do not appear consecutively in the ciphertext. This qualifies these two digits for the side of the MD block . See the next step for the design of our MD block for this cipher.

STEP FOUR – WRITE TEXT IN MD DIGITS.

We have determined that digits 5 and 6 will be our side or row digits in the MD block. Our MD block will look like this:

                                0   1   2   3   4   7   8   9
                                                             (Single digit row)
                           5
                           6

The very first row beneath the MD top digit row are MD text single digits. The rows beginning with side digits 5 and 6 will be two digit MD text with MD digits in the 50’s and 60’s. We write our MD text by posting two digit numbers for all digits beginning with 5 and 6 and one digit numbers for all others. The MD text follows.

 7 53  8 59 51  2  4  7 67  8  2  4 64  3  7 64  1 64 64 63  8  2  3 51  9  1  9  2  9

59  9  0  0  4 61  9  4  9 61 64 58  9  3  4 51  3 57  8  7 53  8  3  9 52 64 68  8  3

53  9 63  8  7  2 51  8 52 51  7  7 61 64  7 53 51  2 52  4  4 69  2 63 51 63  8 52    

9  4 52 51 52  9 60 64 69  3  1 54 64 60 61 51  7 53 64  3  0 60  9  0 51 59  8

63  8  4  7 61 53 64 61  9  4  4 61  8 67  7 64 63  8  2  7 53  8 59  9  0  0  4  9 59

7  8  2  9 54 64  9  7 51  3  1 58 51  4 53  9 67.

STEP FIVE – PERFORM FREQUENCY COUNT OF MD DIGITS.

Count the frequency of the MD digits above and post them to the MD key block. This will be helpful in the locating of high frequency plaintext letters in the completion of the plaintext. The MD digit frequency count for this cipher looks like this:

                                0   1   2   3   4   7   8   9
                               6   4   9   9  13 14 16 19      (Single digit row)
                         5 - 0  12  6   8   2   1   2   5
                           6 - 3   6   0   6  13  3   1   1

STEP SIX – LOCATE CRIB.

Coupling the JA, E-13 cipher’s title, “There are no better uses for barrels” and the crib word of “falls”, I developed the extended crib of “Niagara Falls.” It is the time to search for the proper placement of this crib. Look for consecutive digits to place the two “l’s) in Falls preceded by three like digits, properly spaced, to represent the “a’s” in Niagara. You will find this proper spacing at the end of line one and beginning of line two of the MD text.

 7 53 8 59 51 2  4  7 67  8  2  4 64  3  7 64  1 64 64 63  8  2  3 51  9  1  9  2  9
N I A G A R A

59  9  0  0  4 61  9  4  9 61 64 58  9  3  4 51  3 57  8  7 53  8  3  9 52 64 68  8  3
F A L L S

STEP SEVEN – FILL IN KNOWN PLAINTEXT IN MD TEXT.

 

 7 53  8 59 51  2  4  7 67  8  2  4 64  3  7 64  1 64 64 63  8  2  3 51  9  1  9  2  9
         F  I  R  S           R  S     N        G              R N  I  A  G  A  R  A
59  9  0  0  4 61  9  4  9 61 64 58  9  3  4 51  3 57  8  7 53  8  3  9 52 64 68  8  3
F  A  L  L  S     A  S  A           A  N  S  I  N                 N  A              N
53  9 63  8  7  2 51  8 52 51  7  7 61 64  7 53 51  2 52  4  4 69  2 63 51 63  8 52    
   A           R  I        I                    I  R     S  S     R     I
9  4 52 51 52  9 60 64 69  3  1 54 64 60 61 51  7 53 64  3  0 60  9  0 51 59  8
A  S     I     A           N  G              I           N  L     A  L  I  F
63  8  4  7 61 53 64 61  9  4  4 61  8 67  7 64 63  8  2  7 53  8 59  9  0  0  4  9 59
      S                 A  S  S                       R           F  A  L  L  S  A  F
7  8  2  9 54 64  9  7 51  3  1 58 51  4 53  9 67.
   R  A           A     I  N  G     I  S     A

STEP EIGHT – POST LETTERS TO MD KEY BLOCK AS YOU UNCOVER PLAINTEXT.

                                0   1   2   3   4   7   8   9
                               L   G   R   N   S        A     (Single digit row)
                           5 I F
                           6

The known crib letters are now posted to the MD key block. As additional plaintext letters are found, continue to post them to the key block. This will be helpful in the keyword recovery process. Use the MD key block frequency count from step five to uncover further plaintext letters.

STEP NINE – THIRD ROW OF MD KEY BLOCK IS END OF ALPHABET.

One of the biggest weaknesses of the Monome-Dinome cipher is the inflexibility of the key block arrangement. Since the key block is always one of a horizontal arrangement, we can look for the end of the alphabet letters on the third line and begin to make some very good educated guesses on low frequency letters. Look for these low frequency letters. MD digits, 60,  67, 68 and 69, representing plaintext letters, P, U, Y and Z are both obvious and helpful in this cipher.

STEP TEN – ARRANGE MD KEY BLOCK ALPHABETICALLY TO OBTAIN KEY WORD.

Once again, the inflexibility of the horizontally designed MD key block proves to be very helpful in our key word search. After filling in the gaps of the remaining plaintext with some creative anagramming and back and forth help from the MD key block, we are ready to search for the key word.

With all of our plaintext letters posted to the MD key block, we need only to look at the last row of the key block to put our key word in its proper order. Alphabetically arranging the third row of the MD key block will alphabetize the entire block and produce the key word.

Look no further if you wish to complete the solution on your own.

MD Key Block Sequential Order:

                                0   1   2   3   4   7   8   9
                               L   G   R   N   S   T E   A     (Single digit row)
                           5 K I D H B C M F
                           6 Y W Q V O P Z Y

MD Block Alphabetical Order:

                                4   7   2   9   3   1   0   8
                              S  T  R   A  N  G  L  E      (Single digit row)
                           5 B  C D   F   H  I   K  M
                           6 O  P Q   U   V   W  Y  Z