SOLVING CIPHER SECRETS

M ORE than three centuries ago Sir Francis Bacon, speaking of secret writing in his "Advancement of Learning," stated that one of the virtues of ciphers was "that they bee not laborious to write and reade."

This property would seem to be greatly desired in all ciphers; and especially if they are to be used under adverse conditions. Kerckhoffs (1883), the French writer on cryptography, has this to say, for example, of the military cipher: "In view of the circumstances attending its use, it should be easy to operate, and not demand mental strain, nor the knowledge of a long series of rules."

And Bazeries (1901), another French author on the subject, holds the same opinion, advising that ciphers in general, and military ciphers in particular, should be simple and rapid in use.

Under favorable circumstances the use of a complex or burdensome system might be allowable. But the consensus of opinion is, as it quite evidently should be, overwhelmingly in favor of the simple, easy, and rapid cipher.

These few remarks are with special reference to the fourth of the ten cipher essentials, published in FLYNN'S WEEKLY for May 28. Desideratum No. 5, relating to cryptographic equipment, will be taken up next week.

The task of correctly grouping the symbols in last week's No. 27—which was really more on the order of a puzzle than a cipher—provided a valuable, and what should have been a highly entertaining, cipher exercise.

The omission of the dot (.) separators rendered this cryptogram somewhat like a message mutilated in ordinary telegraphic transmission by false divisions in the Morse code symbols. The following example, showing how "TRY" could be sent "KEY"—or vice versa—by a false spacing of the elements of the first two symbols, is an illustration of this so-called mutilation in International Morse code:

T -  R .-.  Y -.--
K -.-  E .  Y -.--

In the present case, however, since the symbols of the Gustavus Selenus alphabet contain from one to six elements, a start can be made by taking from one to six of the first signs in the cryptogram as possible symbols for the first letter of the message: - (A); - - (not used); --- (C); ---- (P); ----- (G): and -----U (not used).

Taking each of these four letters as starters, and rejecting unused symbols and improbable combinations, the following possible two-letter beginnings are similarly obtained: AC-AP-AT-CA-CE-PA-GO. Probable values for the third and subsequent letters may be found in the same manner.

Solving this cryptogram may be likened to effecting an escape from an unknown labyrinth. At every turn the "prisoner" finds himself confronted with new passages which he must explore and eliminate one by one until, eventually, he achieves his "escape" by the following route: "Gold is to be shipped Friday. Have the gang ready." Did you observe that the original alphabet for this cipher, published last week, used the same symbols for L and T, and for K and U-V?

The weak spot in No. 28 was the Bazeries "shift" symbol, only two candidates for which—J and A—appeared in the cryptogram. Of these "A" was the more likely, since it occurred both as a single (AKA) and doubled (AAWKAA) letter.

Taking "AKA" at the end of the cryptogram as a probable substitute for the period (KAK), gives two symbols in the cipher alphabet, and suggests an alphabet of coupled pairs, thereby greatly facilitating the discovery of additional symbols by the usual methods. The alphabet was based on the keyword "HEADQUARTERS," as follows:

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

Message: An important conference about the Blake murder will be held at headquarters at 10 (KKABKK ) tonight. (KAK). Be there without fail. (KAK)

Although No. 29 (by "C. E. R.") is in theory a double substitution cipher, in practice both substitutions can be performed mentally at a single operation, rendering the system easy to use.

At the first substitution the message letters are represented by their place equivalents in Roman numerals: A=Ⅰ B=Ⅱ... Z=ⅩⅩⅥ. At the second substitution, the Ⅰ's of these numerals are replaced by the letters A to I, inclusive, selected at random; the Ⅴ's, by the letters J to V; and the Ⅹ's, by letters W to Z.

Each group thus stands for one letter. For example, DS—which equals Ⅳ—represents D, the fourth letter of the alphabet. Similarly, ZK equals ⅩⅤ, or O; and so on. This cipher affords a large number of substitutes for each letter, and may be varied, for individual use, in one or both alphabets.

What it gains in variety, however, it loses in economy; the cryptogram being several times longer than the message, with the short groups—instead of the customary "fives"—tending to make it still more costly, in the event of telegraphic transmission.

So much for last week's ciphers. This week's lot offers you some choice problems. No. 30 is a simple substitution affair; not difficult, but short and interesting. No. 31, submitted by a veteran contributor to these columns, offers a distinct novelty in transposition ciphers.

No. 32 is based on fragmentation of the International Morse code. The short example of "mutilation" given above may suggest the principle of this cipher. But to assist in working it out, a methodized arrangement of the International Morse code is subjoined. The foreign language symbols for ü, ä, ö, and ch, may be required in this cipher, although they do not happen to be needed in the present example:

This last cipher illustrates an elementary use of the multifid symbol, which occupies an important place in the development of modern ciphers. Unlike No. 27, above, however, the present example, with the key, is certainly decipherable:

CIPHER No. 30 (Paul Kirby, San Diego, Calif.).

TSEWHOHS  OBF  KAG  OFS  XAEH
RSOF  OBP  KAG  OFS  TOXR  PSOP
OXFSOPK.

CIPHER No. 31 (J. Levine, Los Angeles, Calif.).

BESPON  FO  TE  DERRADAT  FAH
NOI  UNREEOR  INDTUTETSUEBS  BNIN
YIACOD  XS  TEE  ROSSOTECT O
POPIHINY.

CIPHER No. 32.

ESUIB  DOGKI  ESNVR  TISKH
NEKEU  SERDS  RDEUM  MAEEM
SIHKE  NJDTS  KI.

The translations and complete explanations of these ciphers will be published in the next issue of FLYNN'S WEEKLY.

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