Re: AW: VMs: context sensitive encoding

[Nick Pelling <incoming@xxxxxxxxxxxxxxxxx>]

Hi Claus,

At 08:38 20/03/03 +0100, Claus Anders wrote:
> BUt I think now, if you encode a text with cipher, no coding algorithm 
> exists, which can lower the h2 entropy of a given text to the VMS level 
> without lengthen the text.My conclusion is, if the VMS is a cipher, the 
> original language has to have the same low h2 entropy too.As the average 
> token length is short (compared to most known languages), there can only 
> be few 'nulls'.I don't believe (but has to be proven), that a few nulls 
> can lower the h2 drastically.

Here's an idea: how about a syllabic cipher (similar to Japanese), but 
which is expressed as.pairs of letters from a (fake) alphabet. Something 
like...

        pa      <-->    fc
        pe      <-->    of
        pi      <-->    ol
        po      <-->    cc
        pu      <-->    ee
        (etc)

Many of the more complex ciphers in the Milanese chancery ledger (most 
notably the very first, the Tranchedino's own cipher for communicating with 
Milan's envoy in Florence, which [I can only presume] evolved to its level 
of complexity over a number of years) have a large number of cipher symbols 
for common syllables (like quo, que, qua, etc). So a syllabic cipher is 
perfectly consistent with a 1450-1460 dating. In fact, a pure syllabic 
cipher would be the logical extension of this

We also have evidence even as early as 1440 of ciphers that  use pairs of 
letters in a misdirecting alphabet, so a cipher based on pairs of (fake) 
letters would also be consistent with the same dating - the only "novelty" 
(and I don't think it would be that great a novelty) here is the 
combination of the two.

If the code-maker were to do a frequency analysis of pairs of letters of 
even a single page of normal MS text, it would be quickly clear which 
combinations came up most often, and he/she would then be able to allocate 
fake letter-pairs on the basis of maximal misdirection and confusion.

And the punchline? This would decouple the fake alphabet's statistical 
distribution from the real alphabet's statistical distribution - a 
fifteenth century cryptographer's dream! Anyone performing analysis on the 
apparent alphabet would then see only what the code-maker wanted them to see.

Comments?

Cheers, .....Nick Pelling.....

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