Students how basic encryption types work. The students can send encrypted messages to each other.
| Learning Scenario Identity | |
| Title | JYU29: Substitution Encryption |
| Creator | JYU |
| Length | 90 minutes (2×45 minutes) |
| Main idea/description | Students how basic encryption types work. The students can send encrypted messages to each other. |
| Target group | 3rd-6th grade |
| Curriculum/learning subjects | Mathematics, Physical Education, ICT |
| Competencies | Students will learn how data can be encrypted and decrypted. |
| Teachers’ wellness competences | TC4: Social e-competency |
| Learning Scenario Framework | |
| Pedagogical method | PI3. Enforcing attention and Awareness |
| Software/materials | In this scenario, students will work in pairs to encrypt and decrypt messages using substitution encryption, learning about basic encryption methods and data security. The goal is to understand how substitution encryption works by replacing each letter with another according to a predefined system. Teacher Tools: A conferencing tool with breakout rooms can be used for online sessions. The teacher can monitor each pair to ensure instructions are followed correctly. Clear Instructions: Begin by explaining how substitution encryption works—each letter in the plaintext is substituted with a corresponding letter in a cipher alphabet. Provide a simple cipher key (e.g., A = X, B = Y, C = Z) to demonstrate. Use real-life examples of encryption to make the concept relatable. Engagement and Breaks: To maintain focus, incorporate short breaks between encryption and decryption tasks. Use physical activities or mindfulness moments to help students refocus. Gradual Complexity: Start with short, simple messages that are easy to encrypt and decrypt. As students become more confident, increase the length or complexity of the messages. Allow students to create their own cipher keys. Collaboration and Reflection: After each round, ask students to reflect on the process and share their experiences. Guiding questions could include, “What strategies helped you encrypt faster?” and “How challenging was it to decrypt using a key you didn’t create?” Suggested Activity: Encrypt and Decrypt Messages: Students work in pairs—one encrypts a message using a cipher, and the other decrypts it using the key. After the message is decrypted, switch roles.Error Handling: Introduce deliberate mistakes in the cipher to simulate real-world challenges where errors need to be identified and corrected.Closing Reflection: After completing the exercise, hold a discussion: “How does substitution encryption relate to modern data security?””What challenges did you face when decrypting messages?”This approach ensures engagement, minimizes technostress, and promotes hands-on learning through gradual complexity and reflection. |
| Evaluation tools | The teacher observes the pairs as they start to work on the assignment. The teacher also follows the discussions after each assignment. |
| Learning Scenario Implementation | |
| Learning activities (description, duration, worksheets) | IntroductionExplain the concept of substitution encryption compared to Caesar Cipher (if you have completed the scenario already): Substitution encryption and Caesar cipher are both methods of encrypting text by replacing letters with others, but they differ in how the replacements are made. In a Caesar cipher, every letter in the message is shifted by a fixed number of positions in the alphabet (e.g., A becomes D if shifted by 3). The key is always the same for each letter, making it easier to decode if the shift pattern is identified.Substitution encryption, on the other hand, uses a unique cipher where each letter is substituted with another letter from the alphabet, but the substitutions are not uniform or based on a simple shift. This random mapping of letters creates a more complex encryption because there is no predictable pattern, making it much harder to break compared to the Caesar cipher.Substitution encryption is more secure because even if a few letters are decoded, it does not reveal the pattern for the entire message, unlike the Caesar cipher, where the entire alphabet follows the same shift. In short: Each letter of a message is substituted with another letter based on a predefined cipher key. In this exercise, students will work in pairs to encrypt and decrypt messages using substitution encryption. One student will encrypt a message while the other decrypts it, promoting teamwork and problem-solving. Exercise 1: Pair Work with Substitution Encryption Pair Up and Assign Roles:Each pair of students will have one “encryptor” and one “decryptor.” The encryptor uses a provided cipher (e.g., A = M, B = N, etc.) to encrypt a short message. The decryptor must use the same cipher to decode the encrypted message.Only the encryptor is allowed to write or manipulate the message, while the decryptor reads and interprets. Step-by-Step Encryption and Decryption:The encryptor writes a short message using plain text (e.g., “HELLO”), then substitutes each letter according to the cipher key.The encryptor passes the encrypted message to the decryptor, who uses the cipher key to reverse the encryption process and reveal the original message.Repeat with several short messages to build familiarity with the process. Mindfulness Breaks:After each message is decoded, take a brief mindfulness break (e.g., deep breaths or a quick stretch) to reset and reduce cognitive load before moving on to the next message. Switch Roles:After the break, switch roles so that the decryptor becomes the encryptor. This gives both students the opportunity to experience both tasks, enhancing learning and engagement. DiscussionAfter the first round of encryption and decryption, gather the students for reflection:”What strategies helped you encrypt faster?””What challenges did you face in decrypting the message?” Exercise 2: Increasing Complexity with Longer MessagesNew Task:In the second exercise, students will encrypt and decrypt longer messages. The encryptor writes a longer message (e.g., a full sentence) and encrypts it, passing it to the decryptor to decode.Introduce the use of spaces and punctuation, making the process more realistic and challenging. Error Handling:Introduce deliberate errors in the encryption process. The decryptor must identify where the mistake occurred and ask the encryptor to correct it, simulating real-world communication challenges. If Students Finish Early:Allow them to create their own substitution ciphers and encrypt messages for other pairs to decrypt. This fosters creativity and reinforces learning. Closing ReflectionOnce all exercises are complete, hold a final group discussion:”How might substitution encryption be used in the real world?””What techniques did you develop to make decryption easier?””How does encryption contribute to data security?”This approach encourages collaboration, ensures gradual learning, and minimizes technostress through mindful breaks and a focus on clear, step-by-step tasks. |
Appendix 1: Substitution encryption example to use in class.
You can ask student’s to decrypt the following message:
“QYHP YQX HOP’X XQCNHTD. GS T, HPT’O HO?”
It says “This is how it’s working. Fun, isn’t it?” decrypted.
Appendix 2: Empty substitution encryption templates