Re: Native American Encryption?!

[tcmay@netcom.com (Timothy C. May)]

Median writes:

> I may be in trouble for not knowing basic literature, but if so so be
> it.  Would a code you created yourself be secure?  If you create your
> own language from scratch, and the 'enemy' never gets something to act
> as Rosetta Stone, is it still not secure?  Or is the "aliens figure out
> our language with lots of computers" cliche bogus?
> 

I want to avoid casually dismissing Median's question without writing
a mini-essay on code-breaking. Especially when so many fine and
accessible (easy to read) books on code-breaking are available.

(To find them, cruise your local library. I recall the Herbert S. Zim
book as being a very fine introduction. Basic, and nonmathematical.
But a good start. I read it in junior high school, many years ago. I
was reminded of it recently, when I think Whit Diffie cited it as an
influence on him as well--he obviously was more influenced by it than
I was, as he went into crypto and I went into physics, a much less
interesting field.)

Basically, word-frequency analysis kill simple codes. Replace the word
"the" with the string "globflq" and it's still going to be fairly
obvious that "globflq" means "the." And so on.

And, as Median mentioned, a few words may become known, in all the
usual ways, and thus a Rosetta Stone has been found.

The issue of communication with extraterrrestrials--some day
perhaps--is an interesting one. I have no idea what work has been done
on "breaking the code" when almost no clues exist. Some SF writers
have explored this idea.

But in summary, codes are a poor approach. The entropy of coded
messages gives clues about the underlying plaintext and eventually the
code falls. Usually fairly quickly.

Ciphers (or cyphers) are superior, as the entropy of the ciphertext
can be very high (roughly, "maximally random," though I don't want to
get into what randomness means here).

Kahn's "The Codebreakers" remains the definitive book. All Cypherpunks
should at least read the paperback abridgment of the original massive
book. "Kahn on Codes" is also pretty good.

--Tim May


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