Re: Re: VMs: More on Cardan grilles

["jan" <hurychj@xxxxxxxxx>]

Hello, 

as I see it, in general the grille can be simply just an arrangement of slots on the cardboard,
be it for words (Cardan), syllables (Gord Rugg)  or even individual letters. Also, the remaining "filling" 
 can  be  either meaningful but superfluous ( i.e. pure steganography), random or even the rest of 
 the  message (as in Fleissner grille).

 I still do not know what of the above features was the original Cardan grille using since the sources 
describing it differ, but if it was for words,  it probably  had uniform  width cutouts and most likely
 aligned horizontally, but irregularly.   The   words shorter than cutout could have been followed with
 the fraction of the  next word or  filling by nulls and longer words could have been split into two slots.

 If indeed  Cardan grille had word slots and the filling was sensical but irrelevant text, then the 
 hiding was perfect (well,  not exactly, words like death, war, treason  or execution will  probably 
 stand out  :-) but with repetitive use, the solution would be rather easy (as you said, the same places will 
 hold the text) and by selecting the slot width and sliding it around text we may after sevral attempt reach 
at least aprt  of the solution). In that case, I would  consider Bacon's steganographic cipher with binary
 coding (using two slightly different scripts)  more sophisticated, non suspect  and easier to handle,  
since it can be used with any text,  without a need to write the sensical but non suspect filling and such 
way it would not be  too   cumbersome, otherwise it would be clear giveaway and not steganography.

If however fractions or  even single letters were put in  the slots, then itmasking would 
require  more sophisticated filling - otherwise it would be rather obvious. On the other hand, 
the solution would be very difficult, if random filling is used. Well, it is a  trede in :-).

In the case of the VM - there was no need to hide the message in the "innocent text" (not to raise 
the suspicion) -  on the contrary,  it was supposed to be obscure bu using strabge script.  
I believe the unknown script  as hiding the text quite enough  so there was no need to bother
 to fill in the sensical text and pure random or quasi random filling could be used with great 
advantage to make the solution quite difficult.  

If the Cardan grille ( with whole words and sensical text filling) was used, the EVA transcript
 would provide  enough info for us to establish at least the language of the VM 
(it would contain the whole words) and maybe some text as well - since the whoel text would make sense. 
So I agree that the Cardan grille was not used.

But the why   to  reduce all our research to that kind of  grille only? Just because Gord called  it Cardan grille? 
It seems to be that some kinds of grilles were already known before Cardan ( my source says since 15th century, Fleissner is sfrom 19th century) and not only for steganography - they are excellent coding devices. One thing seems to be obvious - drooping lines in the VM could not allow the direct use of the cardboard with straight slots neither for writing nor for reading. In both cases, the re-writing had to be used, by the author as well by the reader attempting to solve it. 

One thing can be tried however: if we make the statistics of the "sentence-lengths", then repeating 
lenght numbers may reveal something. But then again, they may  not - especially if no grill was used at all.

Jan 
  
  
=======  You wrote:  
>A practical example from "http://www.rit.edu/~vxr8205/crypto2/cryptopaper.html";
>
>----------begin quote-------------------------------
>Gardan Girlle uses a sheet of cardboard where there 
>are cut word-length holes.  The encoder places this 
>grille on a sheet of paper and writes the secret 
>message in the hoes.  Then the grille is removed 
>and a letter is formed around these secret words 
>to produce a nice sounding letter.  Here is a good 
>example of such: [3]
>
>    "We explore new steganographic and cryptographic 
>algorithms and techniques throughout the world to 
>produce wide variety and security in the electronic 
>web called the Internet".
>
>By taking out the bolded words [they don't show
>in bold letters in the above copy] out of the letter, 
>we get a secret message: "Explore the World Wide Web".
>--------end quote------------------------------------
>
>Conclusion? The VMs was not produced by that method.
>
>
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