book cover
From FLYNN's December 3, 1927

SOLVING CIPHER SECRETS

Edited by M. E. Ohaver
DEAR FANS: MAY THIS ARTICLE BRING TO YOUR HEARTS
SATISFACTION. AND TO YOUR BRAIN ANOTHER WRINKLE

A SERIOUS defect of most transposition ciphers is that they permit a number of cryptograms of the same length and key to be combined for solution by the multiple anagram method.

This method has already been employed —see issue of July 3, 1926 — in solving a number of similar transposition cycles of a single cryptogram. Here it will be used to resolve the three supposedly intercepted military messages published last week as problem No. 100. Readers will find it of particular interest in this respect.

Solution by this method becomes more difficult as the messages increase in length, and as they decrease in number. With plenty of material, the mathematical methods of matching letters, as described in previous articles, could easily be applied. Even with only three messages these methods would still prove of value. But in any case solution can often be quickly reached by guessing at the content of the communications.

First, however, it will be necessary to prepare a series of paper slips, numbered serially, and bearing the corresponding letters of the several cryptograms. In this case there will be thirty-one slips of three letters each, as shown herewith:

1  2  3  4  5  6  7  8  9  10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31
E  S  Y  E  D  H  I  L  G  R  N  A  O  S  E  P  V  T  E  R  M  A  T  Y  D  N  A  M  I  I  W  
N  E  M  O  E  E  M  A  I  C  U  I  U  A  S  F  N  T  D  R  M  N  S  O  E  T  N  S  L  I  O  
H  E  O  R  S  E  K  H  P  R  V  S  S  S  E  I  A  O  A  N  U  I  W  A  T  D  E  T  X  N  N  

23 6  1  19 11 15 28 24 7  2  20 12 16 29 25 8  3  21 13 27 30 26 9  4  22 14 18 31 27 10 5
T  H  E  E  N  E  M  Y  I  S  R  A  P  I  D  L  Y  M  O  V  I  N  G  E  A  S  T  W  A  R  D  
S  E  N  D  U  S  S  O  M  E  R  I  F  L  E  A  M  M  U  N  I  T  I  O  N  A  T  O  N  C  E  
W  E  H  A  V  E  T  A  K  E  N  S  I  X  T  H  O  U  S  A  N  D  P  R  I  S  O  N  E  R  S  

Assuming that the messages are of a military nature, such terms as AMMUNITION, ATTACK, ENEMY, et cetera, suggest themselves. The first message, for example, contains all the letters necessary to spell ENEMY. Likewise, AMMUNITION might occur in the second. And either of these suppositions would lead to the solution in this instance.

Words of number or direction, as ONE, HUNDRED, NORTH, et cetera, might also be present. Let us assume, for example, that X in the third message has occurred in SIX, SIXTH, SIXTEEN, or other similar word. Upon examination, S is found in the third line on slips 5, 12, 13, and 14; I, on 16 and 22; and, as you will see, X, on 29.

These seven slips, however, can only be combined in eight ways to form the word SIX. Of these eight combinations, 12-22 - 2 9 and 13-22-2 9 can be rejected because of the improbable sequences AAI and OAI formed in the first line. Trying slips 25 and 28 with the remaining combinations, 12-16-29-25 is found to afford probable sequences in all three lines. Further, by prefixing slip 20 to this series, RAPID and RIFLE are formed in the first two lines.

If desired, this process may be continued until all three messages have been fully deciphered. But in the present type of cipher, a short section of the numerical key thus found will reveal the key length of the cryptogram and the order of the remaining slips.

Thus, the interval of seven occurring between any two slips in numerical sequence in the present series, indicates a key of that length, and determines the order in the entire series, as shown above. It is interesting to observe that the series of numbers obtained for this cipher by these methods is exactly the same as would be used for the same key, and messages of the same length, in the original Myszkowski system.

The numerical order of the first seven numbers of this series will also indicate the order of letters in the key word, as shown below, where the first of the present messages has been set up for encipherment by the improved Myszkowski cipher.

V I C T O R Y
6 2 1 5 3 4 7

T H E E N E M
Y I S R A P I
D L Y M O V I
N G E A S T W
A R D

By this time our readers should be ready to tackle transposition ciphers of this kind come as they may, singly or in bunches. Accordingly two more examples are offered under cipher No. 103. These are of different lengths, but in the same key. Decipher either one and you will have the key.

Cipher No. 97 (D. W. Cotton), of two weeks ago, conveyed the message: "Dear fans: May this message bring to your hearts satisfaction in its solution, and to your brain another wrinkle."

Encipherment was done in two steps: first, by translating the message (a) into continental Morse code (b); and then by substituting (c) characters from the first and second banks of a standard typewriter keyboard for the dots and from the third and fourth banks for the dashes.

(a)  D    E  A   R
(b)  -..  .  .-  .-.
(c)  Mor  e  wa  rm5
(d)  More   warm   5

Last week's No. 98 used the first thirteen letters of the alphabet as substitutes for the last thirteen, and vice versa. The message: " To reveal the smallest part of a secret is to hold the rest no longer in your power."

No. 99 used the subjoined key, where letters in the first row are represented by single figures, 2, 3, 4..., those in the second row by pairs of adjacent figures, 23, 34..., those in the third row by pairs of alternate figures, 24, 35, and so on. The message: " Being sincere in my belief that FLYNN'S is the best magazine published, I will always read it."

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

This week's ciphers include, besides the transposition ciphers already mentioned, an interesting straight substitution cryptogram by Mr. Walker, and a typewriter system by Mr. McCaw. Just as a hint: try some common suffixes with No. 102. A typewriter keyboard is not necessary for No. 102, but it would no doubt hasten the solution.

CIPHER No. 101 (M. Walker, Akron, Ohio).

QGMCDDILCTEGM  QCDBJFCLY  QFJ-
SIXEFU  QCAVILCLLCJM  QGFDECLJS
QCEGM  QFJMOUXJFCI L QFJIAPJFM
QJAGLCIFU  QJFZGCMCXJM.

CIPHER No. 102 (William T. McCaw, Cambridge, Massachusetts).

jqhrq  ——q54  h607w  4d546  d9y4  5wq54
Or64h  hO6e9  rr9d8  o66Ow  Oof4q  r654q
r43j9  h864W  w68e7  qhe6y  9wOh4  gwh04
sd4-6  gOh.

CIPHER No. 103.

(a) ITRUS  YHTDE  IDTSO  IGF
(b) HOTPF  TTOOE  HELCR  THNLH
    BTSIO  RERWD  TWYEY  MRRYH
    KTEUH  TIHEU  LYHOS  GSSOI
    TORVR  AOOEL  EO