The Topic: 
Codes, Ciphers & 
Secret Messages

Easier - 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.
Harder - 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. The technology of such secret communication is called cryptology.
Secret writing has been employed about as long as writing has existed. 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.
Codes for Scouts and Cubs
Ordered from beginner to more difficult, these codes can be used by Scouts and non-scouts of all ages.
A Cryptographic Compendium by John J. G. Savard
This site contains a outline of the various types of cipher systems that have been used historically, and tries to relate them to each other while avoiding a lot of mathematics.
Decoding Nazi Secrets (NOVA Online)
At this site, you learn how the Nazi party coded their messages for privacy. You can even send a disguised message or try to break someone else's code!
The Secret Language by Ron Hipschman
Here is a great explanation of substitution and transposition ciphers.
After exploring several of the websites on codes, encryption, and secret messages, complete one or more of the following activities.
Send a Secret Message. Go to Thunk.Com; start with the 'Learn' section. Then write secret notes to your friends. Sign your name in secret code.
Develop Your Decoding Skills. Visit several of these sites to try your hand at deciphering the encrypted messages. Decipher the code; each letter in a phrase has been replaced by another. The last website is the most difficult. 
What is a cyptogram?
1) Cryptogram Corner
2) Cryptograms
3) Cryptograms
4) Cryptograms of Bart Simpson's Blackboard Writings
5) Cryptoquotes: Cryptograms of Sayings by Famous People
6) Daily Cryptograms
7) Play Cypherspace by Todd Grupe (Grade 7 and above)
Learn Morse Code. First visit sites like Morse Code and the Phonetic Alphabets and Morse Code to learn the key for the Morse System. Then use sites like Morse Code Translator (Boy Scouts of America) and The First Digital code.........International Morse Code to improve your skills.
Websites By Kids For Kids
National Security Agency's Kid's Page
Have fun solving challenging problems.
Science Year's Page on Spies, Codes and Ciphers
Learn how to send secret messages.Also, a site on code making and breaking.
Tales of the Encrypted (1999 ThinkQuest Project)
This website explains the importance, uses, and historical context of cryptography.
Data Encryption (1999 ThinkQuest Project)
This website covers various aspects of data encryption across both local networks and the Internet. 
Secret Code Breaker
Information on cracking secret codes and ciphers.
Several More Websites
This is a student page with many links introducing the history and basic theories of cryptography
and cryptanalysis.
This site covers several different types of encryption currently in use including Caesar and other substitution ciphers, Vigenere, Gronsfeld, Enigma, Public Key encryption (RSA), and Pretty Good Protection (PGP).
Introduction to Cryptography
This page provides an introduction into various cryptographic techniques.
Morse Code and the Phonetic Alphabets
Here you find a complete Morse Code directory including punctuation.
Related Websites:
2) Morse Code Translator (Boy Scouts of America)
This tool converts written text to Morse Code and also can convert Morse Code to written text.
3) Morse Code and Phonetic Alphabets 
4) Morse Code Letters
5) WWW Morse Code Generator
6) The First Digital code.........International Morse Code
National Cryptologic Museum
Here visitors can glimpse some of the people who devoted their lives to cryptology and national defense, the machines they built, the techniques they used, and the places where they worked.
Secret Code Breaker
This website has short articles on codes throughout history, Java-based cipher programs to try, and an online version of the Secret Code Breaker program.
Websites for Teachers
Decoding Nazi Secrets (Teacher's Guide at NOVA Online)
This guide accompanies the program of the same name (Above).
Send a coded message
A Simple Cipher
More Resources
How to Make Invisible Ink (Grade 4-6)
Students learn how to make two types of invisible ink and write a message with each type of ink. They are asked to compare and contrast each type of ink.

secret code
Morse code
Alan Turing
Samuel Morse
Caesar cipher
pig latin
UPC bar code
invisible ink
Vigenere cipher
code book
substitution cipher
police code
web transaction
Bletchley Park
transposition cipher

Created by Annette Lamb and Larry Johnson, 1/99, Updated, 1/01. Update by Nancy Smith 7/02