playfair cipher

pamlyndontravers-deactivated201  asked:

Maybe a stupid question but do you have any book recommendations on cryptanalysis? Thank you

Oh, that’s not stupid. Listen to this… I was about to recommend Simon Singh’s The Code Book, and then just as I was about to hit Post I noticed you specified, ‘cryptanalysis.’ Then I went searching my blog to see what I recommended last time someone asked this, and I guess I didn’t tag the posts or forgot what the tags were, so now I can’t find them. Then I remembered that I once said I was going to write a masterpost about books and resources and such, and then I promptly forgot to do it.

Hmm… Let me get back to you on a book specifically about cryptanalysis. To continue with the stupidity theme, I recently quit my job, with nothing to fall back on, and I’ve been looking for some excuse to not go out looking for a new one. Writing a good, long masterpost might be just what I needed right now.

Both Singh and David Kahn, in his book The Codebreakers, talk a little about cryptanalysis, so they would be a good start if you are brand new to the subject. If you’re asking about cryptanalysis specifically, though, I’m guessing you might want something more in depth than that. I’ve been recommending a website named Practical Cryptography, as the author there is all about breaking ciphers. For each one he gives an explanation about how it functions, what is different or special about it, weaknesses, how to analyze a text for character frequencies, patterns and repetitions, how to use techniques like IoC, and he also shares examples of scripts and programs he has written to automate this analysis.

Also, for about the price of a hardbound book you can join the American Cryptogram Association. You’ll get six issues per year of their zine/newsletter The Cryptogram (here’s a sample issue) and a catalogue of back issues clear back to 1932.

Each issue has articles about cryptanalysis and… oh, a hundred or so ciphers, ranging from simple newspaper style cryptoquotes to middling Vigenere/Playfair type ciphers, and on into the harder stuff like tridigital, foursquare, quagmire, and unique ciphers the members create and submit to challenge each other. Here’s a good resource, a page of tools for analyzing ACA cipher types, made by a member whose nom is Bion. They also have conventions, people to correspond with and learn from. Really good stuff. I feel stupid for having put off joining for so many years…

This is all classical cryptography, of course. If you are interested in the cryptanalysis of modern/strong crypto, then I’m still kinda out of my depth on that.