Examining The Dorabella Cipher with Three Lesser-Known Cryptanalysis Methods

Klaus Schmeh
Freelanced Journalist

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Ingår i: Proceedings of the 1st International Conference on Historical Cryptology HistoCrypt 2018

Linköping Electronic Conference Proceedings 149:26, s. 145-152

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Publicerad: 2018-06-13

ISBN: 978-91-7685-252-1

ISSN: 1650-3686 (tryckt), 1650-3740 (online)


Most mono-alphabetic substitution ciphers (MASCs) can be solved with well-known techniques, like frequency analysis, or hill climbing. However, there are exceptions. It therefore makes sense to look around for additional MASC solving techniques—like the ones described in the book Cryptanalysis by Helen Fouché Gaines. These techniques—vowel detection, digram analysis, and consonant lining—have been almost forgotten since the advent of computer technology. In this paper, two of these methods (the third one is not suitable) will be applied on a famous unsolved cryptogram, the Dorabella Cryptogram, and on an unencrypted comparison text. Although this paper will not present a solution of the Dorabella Cryptogram, a number of interesting insights will be introduced. Especially, it will be shown that one of the methods applied works surpsingly well on the comparison text and that there are still ways to improve this technique. In addition, some interesting properties of the Dorabella Cryptogram will be presented, which might be helpful for further cryptanalysis.


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