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K–12 teaching and learning · from the UNC School of Education

Caesar cipher

http://illuminations.nctm.org/LessonDetail.aspx?ID=L587

A lesson plan for grades 9–12 Mathematics

Provider: National Council of Teachers of Mathematics


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In this lesson, students will investigate the Caesar substitution cipher to decode text using inverse operations. After discussing the multiple methods for decoding secret messages, students work with partners to break simple coded messages. Then, students explore several code breaking techniques and determine the letters that occur most frequently in the English language. Students continue to practice decoding using the Caesar activity sheets. Illuminations provides links to helpful web resources, handouts, and detailed instructions for completing the activity.

Students will:

    Encode a message using the Caesar cipher.
  • Use an inverse process to decode a message.

NCTM Standards and Expectations:

  • Draw reasonable conclusions about a situation being modeled.
  • Develop fluency in operations with real numbers, vectors, and matrices, using mental computation or paper-and-pencil calculations for simple cases and technology for more-complicated cases.

North Carolina Curriculum Alignment