Activity Description Encode and decode messages to determine the form for an affine cipher. Input a message to encode, then input your guesses for the constant and multiplier. Caesar Cipher II is one of the Interactivate assessment explorers.

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Caesar Cipher II

Place in mathematics curriculum:

• practice students' long division skills
• demonstrate the applications of modular arithmetic
• practice the students' logical reasoning skills

This activity allows the user to experiment with encoding and decoding messages using modular arithmetic. This activity would work well in same ability groups of three or four for about forty-five minutes if you use the exploration questions and thirty minutes otherwise.

Preparations for this activity:

• supply some structure for them to use to make reasonable guesses
• help the lower ability groups
• show how to solve two step equations