Cracking the Code: Fun with Codes and Ciphers

In fifth grade, some of my friends and I created a cipher in order to pass notes in class. It wasn’t a terribly sophisticated cipher, but it was effective enough to foil the class busybody, who constantly scanned the classroom for miscreants. Many years later, I ripped through the Sherlock Holmes story The Adventure of the Dancing Men, which reminded me of how much fun codes and ciphers can be. It’s a topic that has a long and interesting history, and instantly captures most students’ attention.

Although the terms “code” and “cipher” are often used interchangeably, they are, in fact, different. Ciphers substitute or rearrange letters in a word, while codes use a system of symbols or signals to correspond to letters or numbers. The process of encoding and decoding messages is called cryptography, and it’s been in constant use by most civilizations since ancient times. Julius Caesar famously used ciphers to communicate with his generals, and Mary, Queen of Scots was executed for treason when her cipher-messages were decoded by an agent of Queen Elizabeth I. In the U.S., Thomas Jefferson communicated via coded messages with Lewis and Clark as they searched for the Northwest Passage, and Navajo code talkers played an invaluable role in secret communications during World War II. Today, military forces around the world still continuously employ codes and ciphers to protect confidential information, and businesses rely on encryption to keep their data secure from unauthorized users.

Introducing kids to the history of cryptography, and the study of cryptography itself, can yield rich rewards. Students can trace the history of codes and ciphers through different eras, practice with famous ciphers such as the Caesar and Vigenere ciphers, and create their own. Puzzling over ciphers and codes uses higher-level thinking and analytical skills, and can be used at all grade levels. Lessons on this topic can easily be incorporated into math, history, language arts, linguistics, and science classes. Best of all, it’s a fun topic that challenges students to think both creatively and logically. Below are three resources on cryptography for various grade levels; be sure to check out Peggy’s companion column for ideas on how to incorporate these lessons and others into your classroom. We’ll also be featuring many more cryptography lessons and activities on our Facebook and Twitter pages throughout the week, so be sure to check those pages frequently.

Code Breaker Math
Subjects: Math, US History, Language Arts
Grade: 2-3
In this lesson, students will correctly answer 26 addition and subtraction problems, and also correctly decipher a coded message. Finally, the students will correctly put a message into code. I like that this lesson includes a brief introduction to the Navajo code talkers of World War II – a story that’s not often covered in history classes, and very rarely at this grade level. The lesson also includes modifications for differentiated instruction – a nice feature for those kids who need an extra challenge. This lesson was produced by Marc Sheehan, who offers a web site devoted to educational topics.

Caesar Ciphers: An Introduction to Cryptography
Subjects: Math
Grade: 6-8
In this lesson, students learn about cryptography, the science of secrets. Students analyze the strengths and weaknesses of the Caesar cipher and use this analysis to both compromise the system and improve it. I love the hands-on nature of this lesson, as students work to crack a cipher without the benefit of an encryption key. This lesson also illustrates how math lessons don’t necessarily have to involve crunching numbers, but can address math skills through problem-solving and reasoning concepts. This lesson was created by Discovery Park, a program at Purdue University for graduate students in the STEM disciplines that focused on creating educational resources to highlight science in everyday life.

Protecting Their Nation: The Navajo Code Talkers in World War II
Subjects: U.S. History
Grade: 9-12
The Navajo Indians rose up in support of our country during World War II by developing and utilizing a secret, unbreakable code of communications. Despite a history of shaky relations with Anglo governments, the Navajo served in the Marine Corps because they believed in protecting their nation, which they understood to be both the Navajo tribal nation, and the United States of America. This lesson describes the history of the Marine Corps’ Navajo Code Talker program, emphasizing how the Navajos’ unique history and culture made the program successful. I like how this lesson focuses on a powerful, but relatively little-known aspect of the Second World War – it’s a shame that more people don’t know about the code talkers. Students also get some hands-on practice in creating and transmitting their own codes. This lesson was produced by the MCRD Command Museum, an organization devoted to the history of the U.S. Marine Corps in the 20th and 21st centuries. In addition to offering tours and history lessons to students in California, the Museum also offers lesson plans and other educational resources.