Code and Cipher Basics

During World War II, the United States needed to find a way to protect their messages from their enemies. They devised a code based on the Navajo language. The soldiers who translated the code were known as Code Talkers.

Code and Cipher Basics
By Maggie

Did you know that secret writing began at about the same time that writing became widely used? In fact, the Arabs first invented the science of cryptanalysis in 700 A.D.

Codes and ciphers have been used to send secret messages throughout history. Secret forms of communication are used by businesses to protect their products and information. They are also used by armies and spies to hide coded orders and information from the enemy.

Cryptography, which comes from the Greek word 'cryptos' meaning hidden, is the science of inventing and deciphering codes. In order to read a coded message, you must have a key. If you don't have a key to the code, you have to figure it out. One way to figure out the key is to find the most commonly used letter in the code. Since the most commonly used letter in the English language is 'e,' you can assume that letter is 'e.' You can then continue to look for other patterns. The science of decoding messages without a key is called cryptanalysis.

Codes and ciphers are not the same thing. When you write a message in code you replace words, phrases, or messages by different words, letters, or symbols. When you translate the message into code it is called encoding. Ciphers, on the other hand, translate every single letter, number, or symbol with a different letter, number, or symbol. When you translate a message using this method it is called enciphering it.

Today cryptography is often used when information is sent over the Internet and cellular phones. Information often needs encryption and decryption so that it is kept safe and people's privacy is protected. For example, when you purchase something over the Internet you probably give the company your credit card number. Cryptography prevents someone from stealing your credit card number or other information. Digital cellular phones encrypt voices in order to stop eavesdropping. Each time you use your cell phone, your cell phone provider needs to know who you are so they can bill the correct person. Each time you make a call, your phone company sends a different random number, called a challenge, to your phone. There is a secret key stored in your phone (which is also known by your phone company). Your phone encrypts the challenge and then returns it. If the response from your phone is the same as your phone company's encryption, then your company knows your call is genuine.

There are lots of interesting ways to communicate secretly. Try creating your own code, and see if your friends can figure out your message. Try to write a story using a cipher. Or make up your own hand signals to us with your friends.

Citations

Books

Hegedus, Alannah, and Kaitlin Rainey. Bleeps and Blips to Rocket Ships. Toronto: Tundra Books, 2001.

Online Resources

Teitelbaum, Jeremy. "Codes and ciphers." World Book Online Reference Center. 2005. World Book, Inc. 2 Mar. 2005. <http://www.worldbookonline.com/wb/Article?id=ar121840>.

Images

Copyrighted clip art images from "Microsoft Office Online" <http://office.microsoft.com/clipart/default.aspx?lc=en-us&cag=1> (October-March, 2004-2005). Clip art only available to licensed users for non-commercial purposes.