Encryption Keeps Your Secrets: Introduction to Cryptography

"Encryption Keeps Your Secrets" is a single 50-minute session suitsble for grades 6-10.  It introduces substitution and transposition ciphers, beginning with the Cæsar Cipher. Students use a codebook, decrypt a message encrypted with the rail-fence cipher, then create a keyword substitution cipher. The presentation is available as a narrated-slide video. The accompanying handout is available as a PDF.