Elementary cryptanalysis

by Helen Fouché Gaines

Figure 73 1 2 3 4 x x . x x . x x x . . x . x x x . x x x . x x . x x x . x x . . x U W Y M N X K A E H X R B Z U V X M U W B Z O Y Z T W H V C X Y A h h h 5 6 7 8 x . x x x x . x x . x x . x x x . x x . x x x . x x x . x . C Y A U Z D B R A H V K B A; Z W S V A H K U Z B K C, M S C X h 9 10 x . . . . . x x . x x . x . x C Y X B S, X V Z Y T R Y C X P.

Further work includes the application of the “force method.” That is, we turn our attention to the cryptogram itself, marking with a small cross, or otherwise, all letters determined as consonants, and placing a dot, or other indication, over all letters determined as vowels. Some vowels become evident as early as stage (c), as here we find both X and Y freely contacting our preliminary group of consonants, and if confirmation is needed, a glance back at set-up (b) will show that both of these are step-up letters. They may be labeled vowels without hesitation.

As to consonants, there are two clear text letters, h and n, which, owing to their many contacts with other consonants, and particularly with the low-frequency consonants (as in the digrams CH, GH, PH, WH, NG, NC, NK, NQ, etc.), will often show up clearly on the consonant-line. Of these two, n will appear largely upon the left side of the line, and h, the more reliable of the two, upon the right side. Examining (d) we find W and H appearing exclusively on the right side of the line, and since, under the rules of the game, no letter may be its own substitute, we may assume here that W represents h.

Further concerning h: An examination of the cryptogram shows that W has occurred twice as the second letter of a word, and the second-position is particularly characteristic of h. Then, assuming that W actually does represent h, we have in the seventh word of the cryptogram an intimation that the letter Z is also a consonant (since formations like AHEAD, AHA, are very rare, and seldom, if ever, occur in long words). Thus, we have two new consonants, W and Z, to be added to the consonant-line, with their contacts below, extending operations to stage (e). If desired, the spotted consonants may now be crossed off on the line itself, or merely indicated as in (e). It seems evident from (e), confirmed by (b), that B is our third vowel, and the supposition can be strengthened by inspecting the third cryptogram word, which, at this time, will have appeared as in (f). It also appears from (e) and (b), confirmed by the aspect of the tenth cryptogram word, that R is a consonant. Similarly, M, which, on three appearances, has twice contacted a vowel, may be placed as a consonant. These two new consonants, R and M, are added to the group of known consonants, and all of their contacts are placed on the consonant-line. Our next victim is S, evidently a vowel in spite of (e) because of its position in the seventh cryptogram word (g), which, otherwise, must begin with five consonants in succession. Presuming that a fifth vowel is to be found, the same word suggests either K or H as the candidate. The choice falls on H, according to the fourth cryptogram word (h); and thus continuing the force method with one eye on the consonant-line and the other on the cryptogram, the v-c formation of the cryptogram is finally established as in Fig. 73. Actual identification and solution follow

Figure 74 A text prepared by RUFUS T. STROHM: H Y N W B D │ OMRI, UNKEMPT HELP, BRISKLY SCYTHED BUCKWHEAT ee│eeee t│t CROP. PANICKY SKYLARK UPSHOT; BUMPKIN SHOWED w│ ss│ SMIRK. o│oo l│l Frequency: 8 6 5 4 5 3 4 5 4 6 5 3 4 4 4 3 2 3 2 c│ Variety: 10 8 7 7 7 6 6 6 6 6 5 5 5 5 4 4 4 2 1 kkk│k K P E M R A C I O S H L T U Y N W B D u│uu x x x x x x a│ i│i │h Amplification at step (d) adds P and M. │r │

the usual path of patterns, cross-comparison of words, and inspiration, where all systems are subordinate to the solver’s own perspicacity . . . or “cipher brains.” [Chapter IX] has given some methods for identifying letters from their characteristics, and also mentioned the preparation and use of pattern-word lists.

At this point, it might be well to mention the “vowel-line” method, whose appearance was antecedent to that of the consonant-line. This earlier method was conceived by Erik Boden, and in principle works in reverse to the consonant-line method. Its set-up is like that of the consonant-line except that vowels, instead of consonants, are placed at the top. The contacts made by the determined vowels are listed fore and aft as is done with the consonants in the consonant-line method. The vowel-line shows several letters by certain characteristics . . . a letter appearing exclusively on the left might represent h, and one appearing solely on the right can be taken for n. The liquids, l and r, straddle the line about equally. On the supposition that you have located three vowels, the list of contacts on the vowel-line will not include, or only rarely, any other vowels as yet unidentified. A good suggestion is to use the consonant-line as specified, and then follow up with the vowel-line, using the vowels you have definitely identified as such. The result will be thus: The letter appearing exclusively to the right of the consonant-line will appear solely on the left of the vowel-line, and vice versa. If such appearances are noted, then you have spotted h and n . . . . . identified as suggested in another part of this chapter.

The workability of the consonant-line system in unravelling the mysteries of the “Dizzy” crypt is best judged by making a series of preliminary sheets from clear text. In Fig. 74, for instance, we have the solution to one of the most skillfully manipulated cryptograms in the collection of 130. This was prepared by Rufus T. Strohm as No. 17 Aristocrat of the April, 1932, Cryptogram. The total variety-count is 104, 20% of which is about 21. The line of demarcation thus falls in the group H L T U, each with a variety-count of 5 and no step-down. H, with figures 5-5, could be grouped with the remaining letters, giving us H Y N W B D as consonants, with P and M to be added at step (d). We thus include Y among our sure-fire consonants, and, in fact, it often is a consonant, but this is a problem no solver

Figure 75 A text prepared by J. LLOYD HOOD: D C M P B F Q W J K │ GARGANTUAN MESTIZO ESCORTS JUNOESQUE NEGRO aaaa│aaaa oo│ooo WOMAN ADOWN NIGHT CLUB AISLE. DARK HUED │eeee n│n AMAZON HAD BEAUTIFUL LAPIS-LAZULI PENDANT. ss│ │l Frequency: 14 9 8 6 10 7 6 6 6 4 4 5 3 3 2 3 2 2 1 1 2 1 1 i│i Variety: 12 11 11 9 8 8 6 6 6 5 5 4 4 4 3 3 3 2 2 2 2 1 1 u│uuu A E U I N O L S T G R D H Z C M P B F Q W J K r│ x x x x x x x x x x Amplification at step (d) adds T, G, H, and Z.

has yet been able to overcome. However, the letter Y can usually be spotted by position. Note that except for Y, every vowel here is a step-up letter.