Introduction Overview

This module introduces Chapter 5, Vigenère Ciphers. The Vigenère cipher was used during the American Civil War. One difference between this cipher and the ciphers studied so far is that it cannot be cracked with ordinary frequency analysis. In fact, it was once thought to be unbreakable, but students will learn how to crack it using middle-grade mathematics.

In working with this cipher, students will combine many mathematical skills and build confidence in solving complex problems.