Cryptography Reference
In-Depth Information
More complicated grammars might look like this:
Start
noun verb
noun
Fred
Barney
verb
went fishing where
went bowling where
where
in direction Iowa.
in direction Minnesota.
direction
northern
southern
For simplicity, each of the productions in this grammar has two
choices— call them 0 and 1. If you begin with the Start variable and
always process the leftmost variable, then you can convert bits into
sentences from the language generated by this grammar. Here's a
step-by-step illustration of the process:
Step
Answer in Progress
Bit Hidden
Production Choice
1
Start
none
Start
noun verb
2
noun verb
1
noun
Barney
3
Barney verb
0
verb
went fishing where
4
Barney went fishing where
1
where
in direction Minnesota.
5
Barney went fishing in
0
direction
northern
direction Minnesota.
The bits 1010 were hidden by converting them into the sentence
“Barney went fishing in northern Minnesota.” The bits 0001 would
generate the sentence “Fred went fishing in southern Iowa.” The bits
1111 would generate the sentence “Barney went bowling in southern
Minnesota.” There are 2 4 different sentences in the language gener-
ated by this grammar and all of themmake sense.
Obviously, complex grammars can generate complex results and
producing high-quality text demands a certain amount of creativity.
You need to anticipate how the words and phrases will go together
and make sure everything fits together with a certain amount of fe-
licity.
Figure 7.1 shows the output from an extensive grammar devel-
oped tomimic the voice-over froma baseball game. The entire gram-
mar can be requested from the author.
Figure 7.1 only shows the first part of a 26k file generated from
hiding this quote:
I then told her the key-word which belonged to no lan-
guage and saw her surprise. She told me that it was im-
possible for she believed herself the only possessor of that
word which she kept in her memory and which she never
wrote down. . . This disclosure fettered Madame d'Urfe
to me. That day I became the master of her soul and I
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