Viewing Single Post From: Double cipher challenge

Viewing Single Post From: Double cipher challenge
jdege	Aug 13 2007, 04:29 PM
Elite member Posts: 263 Group: Admin Member #246 Joined: December 7, 2006	catish10 Aug 13 2007, 08:47 AM Hi, So I'm looking at a Quagmire type cipher? Oh no! I've been reading through the Lanaki lessons at the moment. Can someone explain how lesson ten works where Lanaki lists all the occurances of each cipher letter and their position. Works out the difference and then creates a table of factors. I understand how to get to the factors, but I dont understand which ones are written down, and how, in the example he gives. I was playing with this just to try and confirm the period for the cipher. Michelle If it's Vig with mixed alphabets, are they all the same mixed alphabet? That is, do the multiple alphabets differ from each other by only a shift? Then one effective technique is to simply line them up. Generate frequency distributions for each of your alphabets. Then taking two alphabets at a time, shift one against the other, one character at a time, using the chi test to determine how strongly they correlate. If there's one value that shows a strong correlation, odds are the two alphabets are the same alphabet with that relative shift between them. Not all alphabet pairs will show a strong correlation, if your ciphertext is short. But some will. For the ones that do, combine them by shifting one against the other, and sum their frequency counts. The summed frequency distributions will be based on longer plaintexts, and will thus show stronger correlations. Continue doing this until you've collapsed all of the alphabets into a single alphabet. It's IC should indicate that it's a simple substitution. Apply the shifts you've discovered to the ciphertext, and you're left with a simple substitution. (This technique is, IIRC, discussed in Sinkov).
	When cryptography is outlawed, bayl bhgynjf jvyy unir cevinpl.

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