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

By Helen F. Gaines

ISBN-10: 0486800598

ISBN-13: 9780486800592

Contains "166 cryptograms."

summary: comprises "166 cryptograms."

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

Example text

Figure 11 The key, used exactly as described, is a “taking off” key, and this is the common way of using one. It can, however, be used for “writing in” the successive units, placing the first letter of a given unit beneath number 1, the second letter beneath number 2, and so on until the seventh letter has been written below number 7, afterward beginning with the first letter of another unit below number 1 again. Under this plan the first unit of our figure, L E T U S H E, would have been written in in the order U L H S T E E.

Trigrams have also been investigated, the favorite positions of individual letters in their own words, average word-length, patterns, and endless other information, some of which is indispensable, and some merely convenient. It will not be possible, in the space at our disposal, to point out all of the uses to which this kind of information can be put; the student is urged to take his cue from the occasional short references made in connection with examples. All ciphers are decrypted by the general methods suitable to their type, and a transposition cryptogram may involve factoring, examination of the vowel distribution, and anagramming, either singly or in combination.

Concerning the decryptment of concealment cipher, we regret to say that cryptanalysis has little help to offer. Fortunately, most of these ciphers depend absolutely on the belief that they will not be recognized as cipher, and once they are so recognized, they present no resistance. In those few cases where the secret message is not at once obvious, it is sometimes useful to arrange the words (or sentences) in columns, or in rows, for a closer inspection. ” We arrange these words in column form, aligned by their initials, as in Fig.

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


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