This method, as mentioned, is intended merely as a suggested means for effecting an entry. The correct identification of only four letters, as we have seen, will make enormous inroads into the contents of a cryptogram.
Other points which will at times prove helpful are as follows: In words of three and five letters, the central one is nearly always a vowel, taking it for granted that the words the and and will never be present in any difficult cryptogram. In the longer words, the favorite positions of the vowels are the two positions which follow the initial letter and the two positions which precede the final letter. The favorite position of I, in fact, is well known as the third-to-last. About half the words used in any written text are of the type called negative, or empty; that is, the pronouns and auxiliary verbs, and particularly the various kinds of connectives without which no sentence can be put together. If your cryptogram is an “aristocrat,” you will probably find that most of your prepositions begin with A: amongst, amidst, adown, etc. Every sentence contains a verb, and these are more or less limited in their possible terminations. Any letter used only two or three times, and always followed by the same letter, is good material for Q. With what has been said, the student should have no trouble in dealing with the first fifteen “aristocrats” which follow the [next chapter]. As to the remaining thirty-five of Mr. Lamb’s collection, we need say only this: It is impossible to avoid every characteristic of the English language and still write English.
The General Case. — Now let us examine carefully Fig. 64, where the foregoing cryptogram is repeated without its word-separations, and is followed by its frequency and contact data. The various devices indicated in this figure are all of a more or less optional nature. Concerning the preparation of the cryptogram itself, the chief requirement is that it be done in ink, or typewritten, on paper which
| Figure 64 5 10 11 3 3 2 1 9 4 4 2 11 10 1 10 6 4 9 6 2 1 3 10 4 F D R J N U H V X X U R D M D S K V S O P J R K 5 10 3 5 5 3 4 1 6 11 11 9 3 1 3 11 3 10 2 11 3 10 5 9 Z D Y F Z J X G S R R V T Q Y R W D A R W D F V 11 4 9 10 11 4 9 3 10 5 6 5 5 10 3 5 11 10 3 3 9 2 9 3 R K V D R K V T D F S Z Z D Y F R D N N V O V T 6 4 6 2 3 9 5 11 S X S A W V Z R Ordinary Frequency Count: 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 2 10 5 1 1 3 4 1 3 2 1 1 11 6 3 2 9 3 4 3 5 Contact-Information: (High-frequency symbols) R D V S F Z K X D.J F.R H.X D.K ..D K.D S.V V.X U.D R.M K.S V.O Y.Z F.J R.Z X.U J.K M.S R.T G.R D.V S.Z R.V* J.G S.R Z.Y* F.R F.Z D.S Z.D R.V* S.S R.V W.A K.D T.X Y.R V.R Y.W W.F K.T X.A A.W V.R N.O V.K T.F O.T (Low-frequency symbols) D.K Z.Y* W.Z F.D R.N G H M P Q Z.. X.S U.V D.D O.J T.Y (Moderate-frequency symbols) J N T W Y A O U R.N J.U V.Q R.D* D.F* D.R S.P N.H P.R D.N V.D R.D* Q.R S.W V.V X.R Z.X N.V V.S A.V D.F* |
will suffer a great deal of erasure. The placing of its frequency figure above each letter is highly recommended, but not vital. Many solvers will underscore all possible repeated sequences, and will indicate in some other manner all reversals of digrams; others will underscore only the repeated trigrams and longer sequences; and still others do not underscore at all, being content to have all of these repetitions and reversals listed before them in the contact data.
As to the preparation of the contact data, most of the expert decryptors seem to prefer the vertical arrangement of Fig. 63 to the one shown here. But, in simple substitution, a full listing, made for all letters, is not necessary in dealing with the average cryptogram. Usually, it will serve the purpose to make a frequency count first, and then prepare a listing of contacts which includes only chosen letters, those of very high frequency and those of very low frequency; with many cryptograms, no listing at all need be prepared. The contact data, however, are valuable. Each pair of contact-letters actually indicates a trigram. Examining, for instance, the listing under R: The first expression, D.J, represents a trigram DRJ in which the central letter was omitted in order to conserve time and space. When we find, lower down in the same listing, another letter D, we see in this a repeated digram DR. Considering the right-hand side of the same listing: When we find K used three times, we see this as a digram RK used three times. By finding its duplication, under K (left side), we are able to see that two of these repetitions are continued as parts of a repeated trigram RKV. In the list of contacts for D, we find a repeated trigram ZDY, which may be traced, under Y, as part of a longer repeated sequence, ZDYF. It is usually best to underscore these longer repeated sequences on the cryptogram; often, they can be identified from the list of frequent trigrams. But repeated digrams, as a rule, are so numerous as to be in the way when noted on the cryptogram itself. With digrams, only those which are repeated oftenest need be underscored; they can nearly always be identified directly from the list of frequent digrams. The solver, then, prepares his cryptogram and sequence data to suit himself, varying his method according to the difficulty of the given example. With this done, his usual method of solution follows the process popularly known as “vowel-spotting.”
The Vowel-Solution Method. — Using this process, the first step is that of separating the vowels from the consonants; the second is that of assigning identities to the selected vowels, and afterward to the most recognizable of the consonants.
For assistance in applying this method, suppose we extract certain information from the digram chart and have this concretely before us in a series of numbered “pointers”:
1. The vowels A E I O are normally found in the high-frequency section of the frequency count; the vowel U in the section of moderate frequencies, and the vowel Y in the low-frequency section.
2. Letters contacting low-frequency letters are usually vowels.