grille cipher

[mskala@xxxxxxxxxxxxxxxxx]

On Wed, 21 Jun 2000, Dennis wrote:
>     This is a "grille cipher".  There's also a "turning grille" cipher where a
> quarter of the message is written, then the grille is turned 90 deg. etc.  This is
> in HF Gaines' book.   It's a "regular transposition" cipher, and as such not very
> secure, not a lot better than simple substitution.  I remember breaking some of
> these as a teenager.  I don't know how old it is.
> 
>     As for the VMs...  One would see a single-letter frequency count like normal
> language, like the VMs, but there would be very few repeated digraphs, trigraphs,
> etc., quite unlike the VMs.

Only if all or most of the letters on the page are plaintext letters,
re-arranged by the transposition.  What I was talking about was a
relatively small number of transposed plaintext letters embedded in a
stream of meaningless material.  If the meaningless material were
generated by a human attempting to write something that looks random,
rather than by something like drawing letters out of a hat, then I
think it might well have the statistical properties we've observed.

Unfortunately, it'd be difficult to distinguish that situation from a book
of pure human-generated randomness.  There are so many ways to select a
few characters from the page that we could extract whatever "plaintext"
from it we wanted and the exercise wouldn't really prove anything.
There's also the cursive nature of the writing - my proposal that it could
be a copy made by someone who didn't understand it doesn't really hold
much water.

But I *do* think it may be worth thinking about the physical position of
VMS writing on the page when attempting to decipher the writing.

Matthew Skala
mskala@xxxxxxxxxxxxxxxxx                   I paid for it, I own it.
http://www.islandnet.com/~mskala/