RE: VMs: Blanks

["Philip Neal" <philipneal_vms@xxxxxxxxxxx>]

> From: "Maurizio M. Gavioli" <mmg@xxxxxxxxxxxxxxxxx>

> the major problem is establishing the blanks. There seems to be a high 
> number of 'half-blanks'

> Now the question:
>
> Does anyone with a greater familiarity with late medieval / early modern 
> cyphers can summarize the status of the blank in them?

> I mean: there are occurrences of cyphers ignoring the blanks altogether?

Hello Maurizio - a very good question.

I knew very little about questions of this kind before I was interested in 
the VMS and what I have learnt since (from authors like David Kahn, Aloys 
Meister and Bernhard Bischoff) has always been with one eye on the VMS. 
However I would claim to know enough to make a sequence of points in answer 
to your question.

a) There are known to exist today only two manuscripts of mediaeval European 
origin, written in ink on animal skin and bound into a codex, which are 
written entirely in an otherwise unknown script.

a1) The two manuscripts are an enciphering of a Latin plaintext by a 
fifteenth century author and the encipherment is the kind of encryption 
called a simple substitution cipher. Somebody bought one of the two 
manuscripts and easily deciphered it, and that happened in the eighteenth 
century. If the VMS was anything so simple it would have been explained by 
now.

a2) There exist today many hundreds of thousands of manuscripts of the same 
description which are not enciphered. A few hundred of them contain isolated 
words and phrases which are enciphered by simple substitution.

a3) Julius Caesar is said to have enciphered real secrets by the method of 
simple substitution. So far as I am aware, no figure from a later period of 
history is supposed to have done do. The surviving mediaeval examples of 
simple substitution do not contain important information.

The status of the blanks? Simple substitution ciphers of this kind use 
blanks to divide the enciphered words.

b) From the fourteenth century onwards the city states of Italy used ciphers 
of a more elaborate kind to encipher their diplomatic correspondence. The 
word diplomatic refers to official letters between ambassadors and heads of 
state. Diplomatic ciphers were not used to encipher entire books.

b1) Historians call ciphers of this kind nomenclators. Cryptanalysts call 
them homophonic substitution ciphers with nulls. These ciphers are augmented 
by symbols whose purpose is to encipher entire words: in technical terms, 
the ciphers are combined with codes.

b2) The use of nomenclators spread throughout Europe from the sixteenth 
century onwards.

b3) Homophonic substitution ciphers were increasingly replaced by the 
different method of polyalphabetic substitution ciphers from the sixteenth 
century onwards. In practice, polyalphabetic ciphers rely on mechanical 
devices such as cipher discs or printed alphabet squares: no  example is 
known from before the introduction of printing.

The status of the blanks? None. Nomenclators, homophonic substitution 
ciphers and polyalphabetic substitution ciphers absolutely never encipher 
the blanks between words as if they were characters. In the age of the 
printing press, a blank was a physical character made of metal like a letter 
of the alphabet, but blanks are never enciphered for cryptographic reasons.

c) Simple substitution ciphers can easily be solved by analysing the 
frequency with which the characters occur. The fact that the encipherers did 
not regard a blank as a character makes it all the easier to solve the 
ciphers.

c1) Homophonics and polyalphabetics were devised for the very reason that 
simple substitution ciphers can be solved by frequency analysis. From the 
fifteenth century onwards, anybody who was sufficiently sophisticated to use 
such a method of encryption would not have enciphered blank spaces as if 
they were characters.

c2) There are reasons of statistics to believe that the VMS is not a product 
of homophonic or polyalphabetic encipherment.

c3) Fifteenth century treatises on the subject of cryptanalysis were written 
by people who knew the principles of homophonic and polyalphabetic 
substitution. However, they only explain how to decrypt simple substitution 
ciphers with blank spaces between the words.

c4) There is reason to think that Arabic authors understood frequency 
analysis long before the fifteenth century Italians. The implication is that 
homophonic ciphers are an Arabic invention and that the Italian development 
of diplomatic cipher is not derived from the earlier European tradition of 
simple substitution.

Therefore my answer to your question is this. Suppose the VMS to be a 
document intended by its author to be decrypted by somebody who knew how to 
do so. If so, it could only have been written by somebody who knew better 
than to encrypt blanks in the plaintext as blanks in the ciphertext.

Philip Neal

_________________________________________________________________
Use MSN Messenger to send music and pics to your friends 
http://www.msn.co.uk/messenger

______________________________________________________________________
To unsubscribe, send mail to majordomo@xxxxxxxxxxx with a body saying:
unsubscribe vms-list