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| jdege | Apr 1 2008, 03:01 PM |
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The 6x6 grid is usually called a Polybius square, after the ancient Greek historian who first described it. There have been many ciphers over the years that have used these. The most historically significant may be the WWI German ADFGVX cipher, which used a 6x6 Polybius square, followed by a transposition. A couple of points: 1. The system as you describe it has only a single square. Most of these systems relied on some sort of keyword shuffle of the alphabet to populate the square. It's easier to remember a keyword than a complete alphabet. 2. If you're shuffling the contents of the square, you get no additional benefit from shuffling the indices. 3. Swapping the indices within each pair gains you nothing. Swapping the indices in every other pair does gain you some. But swapping indices between pairs gives you a fractionated transposition, which makes things considerably more difficult. Are you familiar with the bifid cipher? It's the simplest of the fractionating transpositions: Wikipedia - Bifid cipher American Cryptogram Association - Bifid Cipher Try to visualize how you'd break it. And recognize - it can be broken. All of the ACA ciphers can be broken by dedicated amateurs. It's what the ACA is and what the ACA does. |
| When cryptography is outlawed, bayl bhgynjf jvyy unir cevinpl. | |
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| Can You Break The Unbreakabe? · Challenges | |
12:00 AM Nov 27
