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Re: VMs: "Running encoding" -- Used in period? Properties?

Hi Elmar,

At 10:55 20/02/2004 +0100, Elmar Vogt wrogt:
Inspired by Steve's "Fold the vellum" paradigm, I wondered about some kind
of "running encoding" of any text. (Don't know if that's the right term -- I'll
just call it that.)

The idea is essentially to write down a table of your cleartext letters:
...
Now what you write down is not the sequence of letters, but their relative
positions.
...
Now you encode this _instructions_ how to jump from table cell to cell.
(Essentially, you've got some 26 different moves, so for each move you could
invent one particular symbol. Hint hint.)
...
Now the questions --

I browsed some period encoding schemes, but didn't find anything like that. Is
it true that none of these "running encoding" schemes was ever used? (I
understand they would be vulnerable to the loss of individual letters, but you
could recover by introducing codes to "synchronise", ie to give you absolute
rather than relative positions again.)

My view on pre-1500 ciphers is that they were at heart *robust* - ie, that a code that needed resynchronising would have seemed too "fragile" for them. Even Alberti's code wheel only changed every few words, not every letter (that would have been too scary).

Polyalphabetic schemes aside, there are very few other crypto mechanisms that could have been used - steganography (hiding letters within letters), verbose ciphers (groups of letters coding for shorter plaintext letters) and transposition ciphers (shuffling the order of letters). The problem is that cryptography is also about *imagination*, and there are thousands of imaginative permutations of these... one of which I believe is the VMs'. :-o

Off the top of your head, what would the statistical properties of a text
encoded that way be? Could this possibly explain the high repetivity of the VM,
provided the right code table was used?

Its repetitiousness, maybe - its structure, no. :-(

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


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