Cryptography

Summary

Materials

• Day 7 PowerPoint deck
• Vigenère Cipher Template]
• Vigenere Cipher Template in Word
• Cryptii - Caesar Cipher
• MakeCode Arcade program: Vigenere encode decode
• Homework: Blown to Bits Chapter 5 pages 21-36 Questions
• Homework: Blown to Bits Chapter 5 pages 21-36 Questions in Word

Instructional Activities and Classroom Assessments

1. Cipher Challenge (10 minutes)
2. History of Cryptography and Ciphers explained (15 minutes)
3. MakeCode Arcade Vigenère Cipher programming activity (10 minutes)
4. Group Discussions (10 minutes)
5. Homework

Learning Objectives

Computational Thinking Practice 5.E.

• IOC-2.B Explain how computing resources can be protected and can be misused.

Essential Knowledge

• IOC-2.B.5 Encryption is the process of encoding data to prevent unauthorized access. Decryption is the process of decoding the data. Two common encryption approaches are:
  • Symmetric key encryption involves one key for both encryption and decryption.
  • Public key encryption pairs a public key for encryption and a private key for decryption. The sender does not need the receiver's private key to encrypt a message, but the receiver's private key is required to decrypt the message.

Details

1. Cipher challenge (10 minutes)

• Ask students to use a Vigenère cipher to decode an encrypted message:
  • Display the secret message on the slide.
  • Ask student to decode it.
  • They can use the Cipher template as a blank table to help them decode the message.
  • Give them two hints:
    • It is a Vigenère cipher.
    • The key is a programming tool they use in class.
  • If after five minutes, students have attempted to discover the key to the cipher, but failed, you can provide them with the MakeCode cipher document so they have the key.
  • Then, give them the remaining time to decode the message.

2. History of cryptography and explanation of ciphers (15 minutes)

• Using the PowerPoint deck provided, explain:
  • What is the field of cryptography?
  • The history of cryptography
  • Caesar Cipher
  • Vigenère Cipher
  • Lessons for the Internet age

3. MakeCode Arcade programming activity (10 minutes)

• Using the PowerPoint deck provided, lead students through an example application of a Vigenère cipher used to encode/decode images in MakeCode Arcade.
• Program: MakeCode.com

4. Group discussion (15 minutes)

• Break students into groups of 4-5.
• You can use the Group Generator program to randomly sort students.
• Ask them to discuss the questions regarding the pages they read from Chapter 5 last night.
• When students have finished discussing their answers, ask groups to share their answers to ensure everyone has the correct response.

5. Homework

• Read pages 21-36 of Blown to Bits Chapter 5.
• Students should answer the questions on the Homework: Blown to Bits Chapter 5 pages 21-36 Questions page.