T HE equipment a cipher should employ is largely dependent upon the conditions under which the system is expected to operate. And since conditions are liable to change, a cipher that is satisfactory in this respect to-day might be impracticable to to-morrow.
Proposition No. 5—see FLYNN'S WEEKLY for May 28—put the matter as follows: Any rules, tables, books, apparatus, machines, or other equipment which a cipher might employ, should not be such as to render it impracticable for its intended purpose. But let us see what a few cryptographers have to say on the subject.
August Kerckhoffs, author of "La Cryptographie Militaire," 1883, states that the apparatus of a military cipher should be portable, and easy to operate by one person. H. Josse, French cryptographer and army officer, writes—in 1885—that military ciphers, properly so-called, should require nothing but pencil and paper.
E. Myskowski, in his "Cryptographic Indéchiffrable," Paris, 1902, regulates equipment to suit the purposes of the cipher.
"In commercial correspondence," he says, "when there is no fear of seizure by strangers, written notes, tables, or apparatus, more or less complicated, may be employed according to convenience.
"Military, political, or diplomatic ciphers," he adds, "should be capable of encipherment and decipherment with the sole aid of pencil and paper; all tables should be discarded and replaced by loose sheets, which can be burned afterward. This will gain in security what it loses in speed."
We gather from all this that the ideal cipher for any purpose should preferably be one that could easily be remembered, and used without any special equipment whatever. Many ciphers now in use, however, fail to meet these requirements.
For example, present day diplomatic correspondence, we are to suppose, is largely carried on by code book. And commercial code books are widely employed in business. As to military systems, "pencil and paper," code book, and machine ciphers were used during the World War. The individual, of course, may adopt any system that he chooses.
So much on the score of cipher equipment. Next week we shall consider the question of variation in cryptographic systems, as covered by proposition six in the above mentioned issue.
The solutions to last week's ciphers are next in order. Of these. No. 30 was a substitution cipher conveying the message: "Hesitate and you are lost; fear and you are half dead already." The following alphabet, where A=O, O=A, B=N, N=B, and so on, was used:
A B C D E F G H I J K L M N O P Q R S T U V W X Y Z
In No. 31 the message, "Better to be despised for too anxious apprehensions than ruined by too confident a security," was enciphered by separate transpositions of the vowels and consonants, as follows:
Transcribe the vowels, EEOEEIE ..., and the consonants, BTTRTBDSP ..., separately in lines of a prearranged length, eight letters in this case. Next take the columns so formed, downward by verticals, and from left to right, thus obtaining the transposed vowel series, EOOEEAAAOI..., and consonant series, BSPNFTDRRDTF ...
Finally, recombine in the cryptogram (c) these two series in the same vowel-consonant order (b) that exists in the message (a), following also the normal word divisions.
(a) BETTER TO BE DESPISED... (b) CVCCVC CV CV CVCCVCVC... (c) BESPON FO TE DERRADAT...
In deciphering, the vowels and consonants are counted and transcribed in columns of the proper length to form rows of eight letters. These are read off by horizontals, and recombined in the same vowel-consonant order as exists in the cryptogram to form the translation. This cipher secures the peculiar illusion of an unknown language.
Modern science has developed the theory that the atoms of the various chemical elements consist of different combinations of only two kinds of electrical particles; and that it may be possible to derive one element from another by merely effecting a change in the number and arrangement of these particles.
Similarly, in ciphers we have the "multifid "symbol, consisting of two or more parts, the units of which may, in some alphabets, be modified, transposed, or regrouped, to form other symbols in the same alphabet.
While we hesitate to compare the sublime perfection of the atom with the commonplaces of cryptography, nevertheless, there are a good many systems which are nicely illustrative of how the alchemist of ciphers can transmute his base metal into gold and silver, and these back into base metal, as often as he chooses.
In last week's No. 32, for instance, the letters of the message (a) were first replaced by their equivalents (b) in International Morse code. The series of figures showing the number of units in the symbols of each group of five letters was then reversed (c) and used as a key for regrouping these units into the symbols (d) of the cryptogram (e).
(a) H I D D E (b) .... .. -.. -.. . (c) 1 3 3 2 4 (d) . ... ..- .. -... (e) E S U I B
Message: Hidden words, like buried treasures, are sometimes hard to find.
The first of this week's ciphers. No. 33, is capable of innumerable variations, and yet can be read at sight if you know the key. Perhaps it is not revealing too much to say that this cryptogram conveys a message of fifty-eight letters.
No. 34 is of the same variety as No. 32, explained above, with the exception that a series of figures, instead of a single figure, forms the key in this case. Just try keys of various lengths until the right combination is found.
No. 35 is in a "hand method" of the "pencil and paper" class, devised by Commandant Étienne Bazeries as a military cipher, and described in his book, "Les Chiffres Secrets Dévoilés," published at Paris in 1901.
CIPHER No. 33 (Captain James F. Kemp, London, Ohio).
379979 184638 801526 230421 731832 173387 936645 995425 380280 840200 410931 621596 540420 793244 847627 393605 777622 779829 589580 915120 659289 250285 728535 430951 479818 320682 900201 749357 469942
CIPHER No. 34.
EVAFG ENUXS EIODL EUASS INSNM IAUNS ESEKR HWTUE SOTSN PEAET EU
CIPHER No. 35.
ZFIYM AAYGC TNMET KKGFO WGYAW YFKYT UKLEI MOGME IAGAV GKKDF YONKX TELAE OFCTG
All of these ciphers will be fully explained next week. And among the new ciphers there will be another Bazeries cipher for you to tackle after you have read the explanation.