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| jdege | May 24 2008, 01:11 AM |
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In the absence of any new challenges here, I've been looking at the problems in The Cryptogram that I've never tried before. The ACA has dozens of cipher types, and there are only a few of them I'm really familiar with. One of the low-numbered ones, (which means easy), was a checkerboard. Didn't have a clue what a checkerboard was, so I looked it up. There are two forms. In each, you use a keyword to fill a 5x5 Polybius square. In the simple form, you use two five letter keywords as coordinates, replacing each letter with its coordinate values: In the more complicated, two keywords are used for each coordinate, and letters from either can be used for coordinates, giving you four alternatives for each plaintext letter: This seems to be done both preserving and not preserving word separations. Because this was a low-numbered problem, it was likely the simpler form. And, in this case, word separations were preserved. So, what do we have, here? A simple substitution cipher. Replace each pair of letters with any single arbitrary letter, and you have an Aristocrat. Pattern word search cracked it with ease. In the more complicated form, you have a homophonic cipher. with four ciphertext alternatives for each plaintext letter. The general techniques for solving homophones are statistical, and these puzzles are way too short for them to be of any use. So the best attack I can envision is trying to reconstruct the square. But for the simple form, I'd hardly expect it to be necessary. |
| When cryptography is outlawed, bayl bhgynjf jvyy unir cevinpl. | |
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| Sometimes Things Are Easier Than They Look · General | |
1:38 PM Nov 28
