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Introduction
If you're a fan of puzzles (or even if you're not), this should be a fun
assignment!
The textbook for the course (Network Security: Private
Communication in a Public World by Charlie Kaufman,
Radia Perlman, Mike Speciner, 2nd edition) contains two ciphers:
- On the page immediately following the title page, there is the following
ciphertext:
Si spy net work, big fedjaw iog link kyxogy
- Page 44 contains the following ciphertext:
Cf lqr'xs xsnyctm n eqxxqgsy iqul qf wdcp eqqh, erl lqrx qgt iqul!
These ciphers are simple substitution ciphers of the type that many people
like to amuse themselves trying to solve. Newspapers often publish a daily
cryptopuzzle (along the lines of a daily crossword puzzle) which readers try to
solve -- often during their daily commutes
The Assignment
The assignment is twofold:
- Read Edgar Allan Poe's The
Gold Bug, and Sir Arthur Conan Doyle's The
Adventure of the Dancing Men
Note: Those of you who are not native speakers of English may have some
trouble reading parts of these stories, because they use archaic English
words (I had to look several words up myself), and attempt to represent
characters' accents and dialects (in particular, the freed slave in The
Gold Bug has a strong Southern black accent). You may have to
ask a native English speaker to "translate" for you.
If you can't understand something, please just send me an email and
I'll try to make sense of it for you. Remember, for the purposes of
this assignment, not all aspects of the stories are germane.
- Solve the above two ciphers -- that is, determine the English cleartext
from which the ciphertext was derived.
There are many resources you can use to accomplish the above, including (in
no particular order):
- Your own brain, with paper and pencil.
- In particular, think about what you know about each cipher, in its own
context. You can infer an amazing amount of information, based on
intelligent guesswork, and knowledge of, say, the typical form you would
expect for the plaintext version, based on what function it is
performing, in its own context.
- Also, you can look at the grouping of the letters and infer which
words are likely to be verbs, or nouns, or whatever. In the case
of 2- or 3-letter words, you can probably make a few guesses, so see
whether you can make further progress based on those guesses. What
word(s) might start the sentence or phrase, given its context?
- Punctuation can often be a dead giveaway, and lead to interesting
insights.
- Collaboration with others, to share ideas, and divide up the work.
Don't forget to give credit where it's due!
Once you've tried the above (please try it first, and spend some time on it),
you can resort to other methods:
- Various deciphering tools and programs available from many sources,
including the World-Wide Web. This course web site has some Java
applets which may help.
- Various accounts of deciphering methods and techniques. This also
includes short stories such as ones referred to above.
What to Submit
I am more interested in how you solved the ciphers than the
actual answers (which I already know). Please submit a description of what
you did, which should include:
- Who you worked with, and specifically how you divided up the work of
deciphering the ciphertexts (who did what; how much of that work was
done by whom)
- What plan of attack you used. This may actually be more than one
plan of attack, if one or more plans failed to produce results. I want
to hear about all the unsuccessful attempts as well as the successful one(s)
-- this is often more illuminating than just discussing the successful
approaches. (You learn a lot more from your mistakes than from your
successes!)
- What assumptions you made; what deductions you made, etc.
- How long it took you to solve each of the puzzles
Edgar Allan Poe's The
Gold Bug shows an example of an explanation of how one of the characters
solved his cipher. Have your explanation be of a similar nature, so that I
can understand how you went about solving the problems.
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