VMs: Re: RE: VMS Lookalike encipherment

["J HALEY" <j.haley@xxxxxxxxxxxxxx>]

Hi Brian

Well we also have Alberti who wrote De Componendis Cifris
(on devising ciphers)  in 1467.
http://www.hup.harvard.edu/itatti/8_alberti.pdf
http://www.kirjasto.sci.fi/alberti.htm

The above two links are worth reading.

Here is a very brief summary of the Argenti family involvement
in Papal cryptography.
http://banach.millersville.edu/~bob/math478/History/pope.html

On the subject of null detection I am open minded. Though I
would have to think a little about what you describe to determine
how easy it would be to identify nulls in a verbose cipher. The
first problem is to reconstruct the verbose elements with enough
accuracy in the first place and as Nick Pelling has rightly said
there are some problems with my initial identifications.

Jeff

----- Original Message -----
From: "Brian Tawney" <btawney@xxxxxxxxxxxxxx>
To: <vms-list@xxxxxxxxxxx>
Sent: 12 July 2005 16:35
Subject: VMs: RE: VMS Lookalike encipherment


> > Just in case this hasn't been posted before here is a link
> > to my latest work on a VMS type encipherment. I hope it
> > is self explanatory.
>
> If I recall correctly from 'The Codebreakers', many of the strategies you
> describe were used in the most complex codes developed by the Argenti
> family.  In addition, they also used nulls and nomenclators.  They also
> eliminated doubled letters in the plaintext, because those were common
> enough in vernacular Italian to create a weakness in the code, and they
> usually assigned multiple allographs to the vowels to mask their
frequency.
> This is a small difference from the cipher table on your web page, where
> you've assigned three allographs to s,t,u and v.
>
> The Argentis made certain that their ciphers were reversible, too.  So,
for
> example, if AB represented a certain letter, then A could not be a letter
on
> its own, but you might find AC or AD or AEA.  They had a trick for coming
up
> with appropriate bi- and triliteral combinations that would have these
> properties, but I don't remember what it was.  I wonder if that wouldn't
> create the 'ordered' effect though.
>
> I once came up with a test for nulls, and I didn't identify any in the VM,
> though I did identify them in files I generated that had nulls.  The test
> worked like this:
>
> 1.  In a natural language transcribed alphabetically, the frequency
> distribution of neighbors of any letter are going to be determined by the
> phonological properties of the letter itself.  So, for example, the
> frequency distribution of letters that come before and after 'A' will be
> different from the frequency distribution of letters that come before and
> after 'T', and both will be different from the frequency distribution of
> letters in the text as a whole.  'T' will only rarely be followed by 'M',
> for example, while that is much more common for 'A'.
>
> 2.  Nulls have no phonological properties.  If they are randomly larded
> throughout a text, especially in high frequency, then the frequency
> distributions of the letters that appear before and after them should be
> more or less similar to the overall frequency distribution of those
letters
> in the text as a whole.
>
> I probably still have the C++ program I wrote to identify nulls somewhere.
> As I said, I didn't see any in the VM using this test, but I did identify
> them in files I generated.
>
> A variation on this test could be used to identify different ways of
> representing the same letter, if you could correctly identify which
> uniliteral/biliteral/triliteral combinations represented individual
letters.
> If you randomly alternate A with 8, for example, the frequency
distribution
> of neighboring letters should be nearly the same for the two allographs.
>
> Brian
>
>
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