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*To*: Dennis <ixohoxi@xxxxxxxxxxxxx>, VOYNICH-L <voynich@xxxxxxxx>*Subject*: Re: Is the VMs Undecipherable?*From*: reeds@xxxxxxxxxxxxxxxxxxxx (Jim Reeds)*Date*: Mon, 25 Sep 2000 20:06:25 -0400*In-reply-to*: Dennis <ixohoxi@micro-net.com> "Is the VMs Undecipherable?" (Sep 25, 10:01)*References*: <39CF68CA.79A0BA6D@micro-net.com>

About unicity distance. The usual examples apply to classical ciphers, where there is a fixed key space, and a more-or-less given plain text probability distribution. And, of course, a definite algorithm for converting plain into cipher, and back again, under the control of a key. To apply this to the VMS problem requies a stretch or 2, as each of the features mentioned above are subject to question. If the enciphering process involves a continual investment in random choices on the part of the encipherer, one should either abandon the idea of a fixed key space or should contemplate adding an extra source of noise into the enciphering process. Consider the following sort of "cipher": the encipherer is entitled to randomly drop 1 vowel in 3 as she goes along, and to randomly insert one extra consonant in 3; everything is then subject to a simple substitution. Do decipher involves deciding which vowels to supply & which consonants to drop, as well as in figuring out the unknown substitution alphabet. A unicity distance can be calculated for this situation, I suppose, but the simplest formulas seen in hobby magazine articles -- like mine -- will not work. -- Jim Reeds, AT&T Labs - Research Shannon Laboratory, Room C229, Building 103 180 Park Avenue, Florham Park, NJ 07932-0971, USA reeds@xxxxxxxxxxxxxxxx, phone: +1 973 360 8414, fax: +1 973 360 8178

**References**:**Is the VMs Undecipherable?***From:*Dennis

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