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Alberti Wheel Cipher


In this activity, students can create and use an Alberti Wheel to make a coded message.

Use an Alberti Wheel to encrypt and decode secret messages. Leon Battista Alberti invented this device 600 years ago. It is a substitution cypher, where each letter of the message is replaced with a different letter, number, or symbol.

Objectives

  • Discover and practice using mechanisms that will translate messages into secret codes.

Materials

  • Per Student:
    Alberti Wheel template PDF
    cardstock paper
    scissors
    brass round headed paper fasteners

Key Questions

  • This cipher is easy to use but also easy to crack. What modifications could be made to further encrypt the message? (Write it backwards, add or subtract from the matched position, etc)

What To Do

1. Copy the template onto card stock

2. Cut out the two circles

3. Attach the smaller circle atop the larger circle using a brass fastener through the centre points.

Encode a Message

1. Write out a message you want to send

2. Determine a two word code.  No, Mr. or Hi are examples you can use without drawing suspicion.

3. If you choose “Hi”. Align your wheel so the capital letter H matches with the lowercase “I”. Use the wheels in this position to substitute the letters of your message. Using the “Hi” code, the world “science” becomes “dnvoyno”.

4. To decode a message, you need to set your wheel to the same alignment as the originator.

5. Take each letter of the code and look it up on the outer wheel. Write down the letter of the inner wheel to translate it.

Extensions

  • Use the blank template to create a custom code using symbols, numbers or colours on the outer wheel.

Other Resources

Science World | Alberti Wheel Cipher Template PDF