CONNECTION TO LEWIS AND CLARK
Like most persons in powerful positions, President Thomas Jefferson
had his share of enemies. At home, the Federalist political party
strongly disagreed with many of his policies. Abroad, European nations
with colonial possessions in America were suspicious of Jefferson's
views on westward expansion. Rumors that he was planning to send
an expedition to the Pacific Ocean only added fuel to the fire.
Consequently, when Jefferson commissioned Lewis to head up a western
expedition, one of Lewis' tasks was learning to encode messages
that might fall into the wrong hands. Jefferson had reason to be
cautious as the interception of messages was a distinct possibility.
Mail service to the frontier (by horseback, wagon, or riverboat)
was very slow and risky.
OVERVIEW
A brief history of cryptology is presented followed by an exercise
in which students encode and decode a message using the system that
Jefferson taught Lewis.
PURPOSES
- To contrast today's communication technology with that of earlier
times.
- To sharpen students' skills in reading and following directions.
- To emphasize the connection between written language and mathematics.
ADVANCE PREPARATION
IMPLEMENTATION
Introduction
Before we proceed with this activity, we need to take a look at
the vocabulary of codes. The scientific study of encoding and decoding
messages is called cryptology from a Greek word "kryptos"
meaning "hidden." Variations are encrypt (to put
into code) and decrypt (to break a code), cryptography
(making up codes), and cryptanalysis (breaking codes). Other
words commonly used are cipher, encipher, and decipher
which mean roughly the same as code, encode, and decode.
Two other terms frequently used in cryptology are plaintext,
a readable message, and ciphertext, a scrambled message.
It probably wasn't long after human beings developed written language
that they also began devising ways to keep sensitive data from prying
eyes. The long history of cryptology began in ancient times with
the simple substitution of one letter for another. Encryption became
more and more sophisticated through the centuries as advances were
made in technology. Today, encryption involves complex electronic
methods based on intricate mathematics. (Click on TEACHING
AIDS FOR UNIT "M" for resources about the history
of cryptology.)
Although codes were used widely for private communications during
past centuries, the most pressing need for cryptology was to conceal
military secrets in wartime. The Spartans of Greece had a code system
whereby the sender wrote a message on a strip of paper or leather
while winding it around a cylinder. The strip was then unwound and
sent to the receiver who decoded it by winding it around a cylinder
of the very same size. If the two cylinders were even slightly different
in size, the message was garbled. The Romans used the "Caesar
Code," an alphabet substitution system which was relatively
easy to decipher by those who could read. It gradually fell out
of use as more people became literate.
Cryptology began to take on greater urgency in the global wars of
the twentieth century. During WWII, cryptologists in Germany created
a sophisticated mechanical encoding system called "Enigma."
The Enigma code was eventually broken, but deciphering it took the
combined efforts of many brilliant mathematicians over a considerable
period of time. One of the Enigma code breakers was Alan Turing
whose work in cryptology eventually provided the basis for modern
computers. (For more about this gifted mathematician, click on http://ei.cs.vt.edu/~history/Turing.html.)
Ironically, one of the most successful American encoding systems
used in both World Wars was not a mechanical device at all, but
American Indian combatants speaking their native languages. The
Navajo "code talkers" who served in the Pacific arena
in WWII are probably the best known. However, over a dozen more
Indian languages were used as codes and have been identified by
anthropologist William C. Meadows. Two examples are the Choctaw
language used in WWI and the Comanche language used in Europe in
WWII. (For a list of the other languages identified by Meadows,
click on
http://members.tripod.com/~Quohadi/code.html)
Indian languages were chosen because of their complex structures
and because they are not widely known or spoken. In addition, Native
American languages have no linguistic connections with German or
Japanese. (For pictures and more information about Indian code talkers,
click on TEACHING AIDS FOR UNIT "M"
and scroll to Activity M-3, Code Talkers.)
CONCLUSION
The Secret Code of Jefferson and Lewis
In today's electronic world, cryptology is "light years"
away from the secret code of Jefferson's time. Not only has encrypting
become increasingly mathematical and complex, it has expanded far
beyond the military establishment. The widespread use of credit
cards and electronic banking and trading have made encryption a
serious concern for everyone.
Nevertheless, at the time of the Lewis and Clark Expedition, some
comparatively sophisticated cryptology systems were in use. Thomas
Jefferson was very interested in cryptology and even had a device
for encoding and decoding messages called a "cipher wheel."
(For a picture and description of a cipher wheel, click on:
http://www.nsa.gov/museum/wheel.html.)
For the expedition, however, Jefferson used a system that did not
rely on machines. The code Lewis learned could be carried in his
head and activated using only paper and quill pen. The origin of
this system is attributed to French mathematician, Blaise de Vigenere
(Blahz de vee zhun AIR), in the sixteenth century. It is a polyalphabetic
system in that it uses multiple letters rather than simply swapping
one letter for another.
This type of code was widely used in Europe and America for two
hundred years and thought to be unbreakable. Cryptologists are now
able to break it fairly easily, but for the lay person, it is still
a handy code. Today we are going to try our hand at encoding and
decoding a message using the Vigenere system that Jefferson taught
Lewis. (Hand out copies of the CODE/MATRIX
and CODE/WORKSHEET.)
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