Cryptanalysis ; a study of ciphers and their solution by Helen F. Gaines

By Helen F. Gaines

Contains "166 cryptograms."

summary: comprises "166 cryptograms."

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Extra info for Cryptanalysis ; a study of ciphers and their solution

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By reading the final letter of each word, you will find out what Smith actually had to say to Johnson: GET READY TO RUN. That is the null cipher reduced to its elements, though naturally it can be more skillfully applied. Significant letters may be concealed in an infinite variety of ways. The key, as here, may be their positions in words, or in the text as a whole. It may be their distance from one another, expressed in letters or in inches, or their distance to the left or right of certain other letters (indicators) or of punctuation marks (indicators); and this distance, or position, need not be constant, or regular.

Our word decrypt, however, is an innovation borrowed from the modern French and Italian writers, and is somewhat frowned upon by leading cryptologists. , to indicate sequences of three, four, five, etc. letters. Ciphers, in general, fall into three major classifications : 1. Concealment Cipher 2. Transposition Cipher 3. Substitution Cipher Minor types, such as “abbreviation,” are sometimes included, though, to the writer, these have never seemed to be truly of a cryptographic nature. In concealment cipher, the true letters of the secret message are hidden, or disguised, by any device whatever; and this type of cipher, as a general rule, is intended to pass without being suspected as the conveyor of a secret communication.

The writing in or the taking out of a text is said to be done by straight horizontals, or by reversed horizontals (backward), or by alternate (or alternating) horizontals (written alternately in both directions). Similarly, we find ascending, or descending, or alternate verticals; and again the diagonal routes will be described as ascending, descending, or alternate. The route may also be a spiral one, and in this case it is said be clockwise or counter-clockwise. Figure 7 For all of these routes, the point of beginning is nearly always one of the four corners, except in the case of the two spiral routes, which are just as likely to begin with a central letter, particularly when the rectangle is a square.

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