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| osric | Oct 31 2009, 07:12 PM |
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Advanced Member
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Hi there aloos (& anyone else following this thread), I am sorry not to have responded earlier to your comment quoted above. You may be absolutely correct that preceding plain or ciphertext is used in some way to determine the movement of the enciphering disks. This 'autokey' principle, as many have called it, is quite popular in many quarters -- including with mosher  However it is also possible that disk movement is controlled by some other means. Perhaps a textual key, perhaps a pseudo-Fibonacci series... Even in these cases the comments of Byrne jr and of Deavoure and Kruh, concerning the need for absolute accuracy, are highly relevant. For example say a textual key calls for moves of v,w,x,y,z... to encipher a certain 5 letters, and the operator mistakenly moves v,w+1,x,y,z then the decipherer -- following the correct sequence v,w,x,y,z -- will get a garbled decrypt from the 2nd letter onwards. The need for perfect accuracy is present, I believe, independant of how the movement stream is generated, so long as the disk movement is continuous -- and the disk (or disks) are not returned to an initial position after each letter is enciphered, which I have not read that anyone is proposing. There is a problem with using plaintext as a determinant of the movement key in that it can cause repeats in ciphertext for the first 5500 letters of Exhibit 1, which comprise a 55-letter plaintext message repeated 100 times, that are not present in Chaocipher. In this regard the latest paper from Jeff Hill is interesting (progress report #14 at TCCH). He proposes a 2-commutator switching system, activated by the plaintext, and claims it has such a long cycle that it will not cause cipher repeats in Exhibit 1. On my list of things to do is to have a good look at Jeff's system, by building a computer model, enciphering Exhibit 1 and examining the output. I am sure there will be many other people who also will be very interested in Jeff's latest ideas. |
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| Clarification · Chaocipher | |
7:12 AM Nov 28
