Figure 173
A Fractional Substitution Based on Morse Symbols - M.E.OHAVER
The Alphabet, Arranged by Group-Lengths:
E . S ... H .... B -...
T - U ..- V ...- X -..-
R .-. F ..-. C -.-.
W .-- ü ..-- Y -.--
I .. D -.. L .-.. Z --..
A .- K -.- ä .-.- Q --.-
N -. G --. P .--. ö ---.
M -- O --- J .--- ch ----
S E N D S U P
... . -. -.. ... ..- .--. Reverse digits, and re-group:
3 1 2 3 3 3 4 4 3 3 3 2 1 3
.... -.- ... ... .- . --.
H K S S A E G

though it should not be divisible by 2. In the figure, the key-word GENERAL, 7 letters, governs the seriation-length as well as the mixing of the key-square, a feature suggested by Ohaver. The substitution is identical with that of the Polybius square, except that the two units of the substitute are written vertically below the original. Digits are then grouped horizontally in pairs, treating one seven-letter group at a time (if the seriation index is 7), and these pairs are replaced with letters from the same key-square. It will be noticed that we have here a form of polygram substitution, in which one seven-letter group has been replaced with another. Also, that possible errors have been confined by the seriation feature to their own seven-letter group.

Delastelle’s “trifid” cipher was of the same kind, except that a three-unit alphabet was required, resulting in three rows of units. It would have been the same as that of Fig. 4, [Chapter II], but with the French accented E replacing the character &. All combinations of three units must be re-convertible into letters.

Fig. 173 shows a form of “mutilation” cipher once published by Ohaver. Beyond stating that its only key is the group-length (7 in the example), we leave the student to figure it out for himself.

As an example of recent use (1918), we are told on excellent authority that the Germans, for quite a long time during the World War, used a field cipher of the following description: There was a preliminary substitution using a key-square of the Nihilist type, except that the external co-ordinates were letters, and not digits, and were chosen in such a way that the five or six letters used were letters having very distinctive Morse symbols; this was for the avoidance of telegraphic errors. In some cases a 5 x 5 square was used, containing only a 25-letter mixed alphabet, and in others a 6 x 6 square containing a 26-letter mixed alphabet and all of the digits. The preliminary cryptogram obtained from this first encipherment was then written into a transposition block and taken off by columns, using key-word columnar transposition. The cryptograms were not afterward shortened by resubstitution, but were always twice as long as their messages, and never contained any other letters than the five (or six) originally used as co-ordinates. This German Field Cipher proved very effective until finally broken by the great French analytical genius, Georges Painvin.

We shall make no attempt, here, to go into the decryptment of these ciphers. The Delastelle “bifid” is, perhaps, a practical cipher, and the student may try his own hand at analyzing the example. The other examples should give no trouble.

154. By PICCOLA. (Delastelle's "Bifid." - Repeated words: AMERICA(N), ATTEMPT, REPORT, THAT, THE, OF, TO. Other short words: FROM, WITH, BEEN, HAVE. Likely words: REPORT, AGENT, CONFIRM, CABLE, etc).
Q I N H P R M L M G R N B M A H G T O L O O E L O A O D R I N H W R O
A A B M M I M M W I B M D A B T H D I L T H T H I N T L A Q M C A M F
I V N K Y N O F H B I I T R F Q L A D K V Q I N H P R M R B H S L L U
A B M E T S O A A B M M I M M I B P I V R Q F T K H I R D F G N I E M
A B E N I L M M P A S I F I O P L Y C C R C I T W I V W M F G I O O S
O E R O I K Q I E F O V N V M Q T D R S I O E R I B U Q C D O A L L A
P L A A O O C A Q O M E I D C N T I U L O L Z D G.
The mixed alphabet here was placed in the square by straight horizontals. History:
Message intercepted following a report that on the tenth of August an attenpt had
been made to enter the American embassy in a country where Royalists are opposed to
a group of radicals.
155. By PICCOLA. (Fractional. - Not so hard).
3 3 3 2 3 1 1 1 2 3 2 2 1 3 1 1 1 1 3 1 3 3 1 1 3 2 2 1 2 2 1 1 2 3 1
2 3 3 2 1 2 3 3 1 1 3 2 1 1 2 1 2 2 2 3 1 2 2 2 3 1 1 2 2 1 2 3 2 3 2
2 1 2 3 1 3 3 2 3 1 1 2 2 1 3 2 1 2 2 3 2 1 3 1 2 2 2 2 3 2 3 2 2 2 2
3 1 1 1 3 1 2 3 2 1 1 2 2 2 3 2 3 1 3 2 2 2 2 1 2 3 1 2 2 1 2 1 2 2 1
1 2 2 3 2 3 2 2 3 2 2 2 3 2 2 3 3 1 2 2 3 1 2 1 3 1 1 1 1 2 1 3 3 3 3
1 2 3 3 3 2 1 3 3 1 1 1 1 2 2 3 1 1 3 1 1 1 1 1 1 1 1 3 2 2 1 2 3 2 2
2 1 2 1 2 1 2 2 2 3 3 2 2 1 3.

156. By PICCOLA. (Fractional. - Nor is this very hard).
E D C Y B A Z C B Z A V W X C X B A E Y D C B V A E D W B X A E Y Z D
A E Z V W D C A E D X C B Y D Y Z V C B W B A Z V E W X B X A E Y D C
B V A E W D C X A E Y Z D C E Z V D W C B E D X C B Y A Z D C B V W A
A E D C B A E E W D C B X Y D C Y Z B V A B A Z V E W X A E W D C X Y
E D Y Z C B V E D C W B A X E D Z V C B A C B V W A X Y X B Y A E D Z
E Y Z D V W C W E D X C B A D Y Z V C B A D C W B A X E E D C B A V E
D C X Y B Z A E D C B A E W D Y Z C B V A B A Z V E W X E D V W C X Y
X D C Y B A Z C Z B A V E W B A E W D X Y E D X Y C Z V V E D W C B A.