Cryptanalysis

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1. todd8Dec 2020
   Breaking ciphers was one of my hobbies growing up the 60's. I wasn't particularly good at it, but I understood the methods used--I read everything I could find on the subject that was available in the open literature. See the bibliography below if you'd like to try some interesting cryptography on paper and pencil methods.

   In graduate school I studied CS and I proposed to my Ph.D. advisor that I would like to do research into cryptography (this was 1983) and he told me that all the interesting things about cryptography have already been discovered and that I should work on something else.

   In 1983 Byte magazine, volume 3, an article proposed using a program based on the Bazeries Cylinder, see [6, 7], to obtain a practically unbreakable cipher. I didn't own a personal computer at the time, so as soon as I could get together with my best friend, a fellow grad student that owned a PC, we were able to break the cipher in just one evening. (Unfortunately, we were the second to do so and missing out on the $10 prize for the first person that broke the cipher.)

   There are paper and pencil ciphers that are well designed and are much stronger than the Zodiac Killer's ciphers as I understand them. One designed for Soviet spies, known as the VIC cipher, resisted US cryptographers (as far as I know) and is explained in an interesting Scientific American in the July 1966 edition, see [7]. See also [8].

   * Pre-computer age cryptography

   [1] Helen Fouché Gaines, Cryptanalysis, https://archive.org/details/cryptanalysis00hele

   [2] William F. Friedman, Riverbank Publications, https://en.wikipedia.org/wiki/Riverbank_Publications

   [3] William F. Friedman, The Friedman Lectures on Cryptography, https://www.nsa.gov/Portals/70/documents/news-features/decla...

   * Interesting historical information, there are so many to choose from now but two of my favorites (one old and one more recent)

   [4] David Kahn, The Code Breakers, https://en.wikipedia.org/wiki/The_Codebreakers

   [5] Leo Marks, Between Silk and Cyanide: a Codemaker's Story 1941-1945 (this is less about cryptography and more about the practical problems of secret code and ciphers during WWII).

   * The Thomas Jefferson wheel cipher or Bazeries Cylinder

   [6] https://en.wikipedia.org/wiki/Jefferson_disk

   [7] https://archive.org/details/eu_BYTE-1983-03_OCR/page/n3/mode...

   * The (once) unbreakable VIC cipher

   [7] David Kahn, Sci American, Vol 215, No 1 (July 1966), pp 38--47.

   [8] https://en.wikipedia.org/wiki/VIC_cipher

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2. bdrAug 2016
   You might be interested to read "Cryptanalysis: A Study of Ciphers and Their Solution", a 1939 (!) book by Helen Fouché Gaines. It covers a lot of these kinds of variants.
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3. aethertapJan 2015
   If you like this kind of stuff, definitely check out the book "Cryptanalysis - a study of ciphers and their solution" by Helen Fouche Gaines. It has loads of interesting hand ciphers of historical interest, going approximately through WWII. It also has tips for how to break them, and how to approach unknown hand ciphers for cryptanalysis (pretty fun stuff; I'm using it as a fun way to teach my daughter math and programming).
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4. jgrahamcMay 2013
   This is a very simple code to break. Helen Fouché Gaines' book Cryptanalysis (published in 1939) is a good introduction : http://www.amazon.com/Cryptanalysis-Study-Ciphers-Their-Solu...
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5. todd8Jul 2016
   Thanks for the comments. I thoroughly enjoyed Between Silk and Cyanide. A small correction, the Playfair is actually a substitution cipher (mapping diagrams to diagrams) not a transposition cipher. The Playfair is a paper and pencil cipher that can usually be broken by hand with even modest amounts of material[1]. The Playfair (and the Wheatstone bridge) were invented by Sir Charles Wheatstone.

   [1] Helen F. Gaines, Cryptanalysis, chapter 21. https://www.amazon.com/Cryptanalysis-Study-Ciphers-Their-Sol...

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