6.5. Caesar Cipher App

This lesson provides an opportunity to use more complex algorithms and introduces functions and local variables.

CSP Framework
Big Idea 5: Impact of Computing (IOC)
Enduring Understanding IOC-2: The use of computing innovations may involve risks to your personal safety and identity.
Learning Objective IOC-2.B: Explain how computing resources can be protected and can be misused.
Skill 5.E IOC-2.B.5 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. Exclusion Statement (EK IOC-2.B.5): Specific mathematical procedures for encryption and decryption are beyond the scope of this course and the AP Exam.

Professional Development

The Student Lesson: Complete the activities for Mobile CSP Unit 6: Lesson 6.5 Caesar Cipher App.

Materials

• Computer lab with projection system
• Tablets, phones, emulators, or Chromebooks
• Lecture video or slides
  
• Caesar Cipher Tutorial (video or handout)

6.5.1. Learning Activities

Estimated Length: 90 minutes

• Hook/Motivation (5 minutes): Ask students if it's safe to type in a credit number into a website. Tell them to look for https (the s stands for secure) which means the site encrypts the information typed in before it sends it. Tell them they will create a very simple encryption app using Caesar Cipher.
• Experiences and Explorations (75 minutes)
  • Part 1: Caesar Cipher: (15 mins) Introduce Caesar Cipher with the video or slides and have them do the encoding/decoding activity and self-check exercises in pairs.
  • Part 2: Caesar Cipher App: (20 mins) Walkthrough the tutorial either in text format or video format. The tutorial provides a template to help focus on the encryption tasks.
  • Functions: (20 mins)Go over the Functions section of the video or slides and do the quizly exercises as a class or have the students work in pairs.
  • Enhancements (20 minutes): Ask students to complete the enhancements to the app and complete the reflection questions.
• Rethink, Reflect and/or Revise (10 minutes): Review functions. Have students post a reflection on their portfolio and complete the interactive exercises.

AP Classroom

The College Board's AP Classroom provides a question bank and Topic Questions. You may create a formative assessment quiz in AP Classroom, assign the quiz (a set of questions), and then review the results in class to identify and address any student misunderstandings.The following are suggested topic questions that you could assign once students have completed this lesson.

Suggested Topic Questions:

Assessment Opportunities and Solutions

Solutions Note: Solutions are only available to verified educators who have joined the Teaching Mobile CSP Google group/forum in Unit 1.

• Caesar Cipher Exercise Solutions
• Caesar Cipher Finished App including Encrypt and Decrypt (in extension 1)
• Quizly Solutions
• Portfolio Reflection Questions Solutions

You can examine students’ work on the interactive exercise and their reflection portfolio entries to assess their progress on the following learning objectives. If students are able to do what is listed there, they are ready to move on to the next lesson.

• Interactive Exercises:
• Portfolio Reflections:
  LO X.X.X - Students should be able to ...
• In the Caesar Cipher App, look for: procedures, loops, if statements.

Differentiation: More Practice

If students are struggling with lesson concepts, have them review the following resources:

• Review Logo 2 lesson and how they used procedures with parameters
• Use the One Minute Videos on procedures and functions.
• Caesar Cipher Flow Chart created by Peter Shelburne - show the processes of encryption and decryption.
• Caesar Vigenere Cipher App created by David Petty - This template allows students to code the Vigenere Cipher.

Differentiation: Enrichment

There is a challenging optional enhancement.

Background Knowledge: Caesar Cipher

• Wikipedia on Caesar Cipher
• Khan Academy Caesar Cipher video

6.5.2. Professional Development Reflection

Discuss the following questions with other teachers in your professional development program.

I am confident I can teach this lesson to my students.
• 1. Strongly Agree
• 2. Agree
• 3. Neutral
• 4. Disagree
• 5. Strongly Disagree