Crack the Code - Introduction to Cryptography

Work together to crack the code. Learn how spies, banks, and computer experts use encryption to keep secrets safe. 

This class will begin with a brief overview of the history of encryption from ancient history to modern computing. As we progress through each step in the history of cryptography, students will solve puzzles based on codes both ancient and modern.

Eras will include:
- Substitution ciphers of the ancient Mesopotamians.
- Letter frequency analysis of ciphers in 1800s America.
- Polyalphabetic ciphers from World War Two. 
- Book ciphers from Victorian England. 

At each stage, I will demonstrate how to crack a simple cipher and then challenge learners to solve a more complex cipher which uses the same technique. Learners will be encouraged to work in teams and awarded praise and points for cracking their codes.

Once learners have demonstrated understanding of the concepts behind algorithmic encryption, I will describe simplified (but accurate) versions of pre-shared key, one time pad, and shared dictionary ciphers. For each type, I will first demonstrate the use, then moderate as learners race to decrypt a message. This portion of the presentation will refer back to the history of encryption. Learners will also receive worksheets which they can use to make their own codes and challenge friends. 

We will end class by attempting to decipher a three-layer wrapped encrypted message. Learners will be encouraged to share their decrypted messages to the classroom as homework. I’ll be available via classroom discussions and messages after class to answer questions from learners as they attempt to decrypt their messages. 

A PDF of the ciphers is available in the classroom. Parents may also request the answer key if needed.