Secret Codes
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A code is a system of symbols, letters,
words, or signals that are used instead of
ordinary words and numbers to send
messages or store information. A code is
used to keep the message short or to
keep it secret.
Codes and ciphers are forms of secret
communication. A code replaces words,
phrases, or sentences with groups of
letters or numbers, while a cipher
rearranges letters or uses substitutes to
disguise the message. This process is
called encryption or enciphering. The
science that studies such secret
communication is called cryptology.
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Secret writing has been employed
about as long as writing has existed.
Codes have been used throughout
history whenever people wanted to
keep messages private. Cryptology
has long been employed by
governments, military, businesses,
and organizations to protect their
messages. Today, encryption is used
to protect storage of data and
transactions between computers.
Pig Pen Code
Scytale Messages/Cylinder Writing
Lovell’s Cipher
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Lovell's cipher, advocated by James Lovell
of the Committee of Foreign Affairs, is one
of many codes and ciphers used during
the American Revolutionary War.
The following example shows a cipher
table for a keyword "CR". This is the
keyword assigned to John Adams.
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22
C DE F G H I J K L M N O P Q R S T U V W X
R S TU V WXY Z & A B C D E F G H I J K
L
23 24 25 26 27
Y
Z
&
A
M N
O
P
B
What does this message say?
Q
SMEQ DEFPQZED MCQ O&&X!
Navajo Code Talkers in WWII
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Code talkers were United States soldiers
during the world wars who used their
knowledge of Native-American languages as a
basis to transmit coded messages. In particular
there were approximately 400-500 Native
Americans in the United States Marine Corps
whose primary job was the transmission of
secret tactical messages. Code talkers
transmitted these messages over military
telephone or radio communications nets using
formal or informally developed codes built upon
their native languages. Their service improved
communications in terms of speed of
encryption at both ends in front line operations
during World War II.
Enigma in WWI
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Enigma was invented
by German engineer
Arthur Scherbius at
the end of World War
I. The early models
were used
commercially from the
early 1920s, and
adopted by military
and government
services of several
countries — most
notably by Nazi
Germany before and
during World War II.
Other Examples of Codes
American Sign Language
 Mirror Writing
 Morse Code
 Binary Code
 Passwords
 Combination Locks
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Resources
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http://www.cerias.purdue.edu/educa
tion/k12/teaching_resources/lessons_pres
entations/cryptology.html
http://www.nsa.gov/programs/kids/s
tandard/lab/elementary/index.shtml