Overview

In this big, multi-step lesson, students learn how the basic mechanics and underlying mathematical principles of public key encryption work. Public key encryption is the basis for most secure transactions on the internet.

Vocab

• asymmetric encryption - used in public key encryption, it is scheme in which the key to encrypt data is different from the key to decrypt.
• modulo - a mathematical operation that returns the remainder after integer division. Example: 7 MOD 4 = 3
• Private Key - In an asymmetric encryption scheme the decryption key is kept private and never shared, so only the intended recipient has the ability to decrypt a message that has been encrypted with a public key.
• Public Key Encryption - Used prevalently on the web, it allows for secure messages to be sent between parties without having to agree on, or share, a secret key. It uses an asymmetric encryption scheme in which the encryption key is made public, but the decryption key is kept private.

Resources

• (Optional) Public Key Bean Counting - Activity Guide (copy as MS Word, Google Doc)

• Multiplication + Modulo - Activity Guide (copy as MS Word, Google Doc)

• The Internet: Encryption & Public Keys - Video (download)

• (Optional) Public Key Cryptography Recap - Handout (copy as MS Word, Google Doc)

• How and Why Does the Public Key Crypto Really Work? - Resource (copy as MS Word, Google Doc)