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Exhibit 2 Cracking Strategies and Info
Topic Started: Dec 15 2010, 05:25 PM (744 Views)
bruce
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Using the same strategy mentioned in another thread, I wrote a crack that works to discover the alphabets for exhibits 1 and 4, given the plaintexts and ciphertexts. (I'll post the code to http://jgenere.googlecode.com shortly.) As others have mentioned, this same strategy doesn't appear to work for cracking Exhibit 2, possibly because Exhibit 2 wasn't enciphered using the "normal" operation of Chaocipher, as was used for Exhibits 1 and 4.

What's known or speculated about cracking Exhibit 2? Has anyone posted about it, yet?

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How I tried to crack Exhibit 2:

Following the steps Moshe outlined in the thread linked above, since the plaintext doesn't contain the letters K or Z, I simply used segments where the ciphertext used the entire A-Z alphabet, and the plaintext used the entire alphabet without K or Z. There are 2 such segments with 5 holes each, and 21 segments with 6 holes each. (There are no segments with less than 5 holes.) When running the crack, instead of starting with completely blank alphabets, I started with K and Z inserted into the right plaintext alphabet in every possible combination of positions.

Unless my thinking is wrong or if my code has a bug, if Exhibit 2 were enciphered using Chaocipher in the same fashion as was used for Exhibits 1 and 4, then the alphabets should have been discovered following these steps, but they weren't.

How are others approaching this?
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bruce
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Also, I tried switching the translations. That is, I tried cracking it as if the ciphertext could encipher to the plaintext, and the plaintext could decipher to the ciphertext.

Another obvious alternative use of Chaocipher I'll try to crack for is repeated enciphering of the message. For this, I can think of two simple paths to explore: 1. encipher(encipher(plaintext)); and 2. encipher(plaintext), then use the resulting alphabets to encipher(plaintext), again. (There are other more complex repeated enciphering paths.)
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james
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I suppose a possible variation in Exhibit 2 compared with Exhibits 1 and 4 is that the distance from Zenith to Nadir is different, in either or both wheels;
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bruce
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I finally posted the crack I mentioned above to http://jgenere.googlecode.com. The code is included in JGenere Chaocipher v0.1.5a r2011.0503.

Shortly after my previous post in December, the motherboard of the computer I was using for working on this fried, and then I was very busy for months with work. Today, I finally recovered the project files from the old HDD. (I now use SpiderOak for automatic and secure cloud storage back ups.)
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