Public Key Encryption

Public key encryption is an extraordinary recent development that has made internet commerce possible. It allows people to encrypt and decrpyt messages without having to share a password to unlock them. It is hard to believe that such a system could exist, yet this mode of encryption is widely used because it is so easy to set up.

This activity works with two people, but it’s most exciting with a whole class, with everybody else trying to intercept a message sent between two students.

This activity is fairly demanding, and requires students to be careful in the way the encode messages. Also, the samples provided here are aimed at junior high students; some younger students may find it too difficult, and more capable or older students are likely to need more complex “maps” to make the encryption convincing, since the one provided can be solved relatively easily. Balancing the amount of tedious effort required for large maps against the insecurity of smaller maps needs to be done by the teacher, although this issue can be a discussion point for the class, since the goal is to understand the issues around encryption.

Public Key Encryption

Activity description (PDF)

Translations and other versions


Related Resources

Curriculum Links

Great Principles of Computer Science [info]
  • Communication
New Zealand Curriculum [info]
  • Technology Level 3: Technological systems
    • Understand that technological systems are represented by symbolic language tools and understand the role played by the “black box” in technological systems.