Invent a Secret Code

Getting Started

Materials you will need:

• materials to make a poster
• a notebook or a folder

Introduction

A special sculpture stands outside the headquarters of the United States Central Intelligence Agency (CIA) in Langley, Virginia. Carved in the copper sculpture is a message in secret code. The code is so complex that for many years even CIA agents could not figure it out. The sculptor, James Sanborn, provided the secret agents with a challenge they could appreciate.

For the chapter project, you will decode computer writing and write in a code used by Julius Caesar. Then you'll invent a code of your own.

Internet Tip: Go to the Elonka's Kryptos site for more information on this sculpture.

Activity 1: Reading

American Standard Code for Information Interchange (ASCII) is a code used by computers. In ASCII, a number represents each English character. Use the tables below to decode the ASCII message at the right.



Internet Tip: The Simple Substitution Cipher Web page explains the method of transforming a message into a code.

Activity 2: Writing

A cipher is a secret code. To decode it, you must know the key. Caesar Cipher, used by Julius Caesar, substitutes one letter for another by shifting each letter in the alphabet three places: A becomes D, B becomes E, and so on. In Caesar Cipher, dog is written grj. Write a letter to a friend in Caesar Cipher.

Internet Tip: Use the Secret Code Breaker to break the code of your letter after you've written it.

Activity 3: Creating

Codes don't always use numbers or letters. In "The Adventure of the Dancing Men," the detective Sherlock Holmes used deductive reasoning to decipher the code at the right. It substitutes stick figures for letters. Using the substitution symbols of your choice, invent a cipher. Use it to write a message. Don't forget to provide the key!

Internet Tip: Read the story of The Adventure of the Dancing Men to learn how Sherlock Holmes broke the stick figure code.

Finishing the Chapter Project

Make a poster to display the cipher you invented. Explain how it works. Include a sample of the cipher and its English translation. You may wish to use a table to illustrate the cipher's key.

Chapter Project Checklist
Have you done all of the following?

• decoded an ASCII message
• written a letter to a friend in Caesar Cipher
• invented a cipher and made a key
• written a message in your cipher

Reflect and Revise
Ask a friend or someone at home to review your poster. Are your explanations and illustrations clear? If necessary, make changes to improve your poster.

Scoring Guide