Every substitution cipher mentioned so far on this website has been a monoalphabetic cipher. This means that the substitution ciphers use a single substitution alphabet so that each plaintext letter always has the same cipher equivalent. In the 1500's Blaise de Vigenere developed one of the first polyalphabetic substitution ciphers. Polyalphabetic substitution cipher refers to any cipher based on substitution, using multiple substitution alphabets.
The Vigenere Square (as seen below) consists of 26 arrangements of the English alphabet. Now, refer to the Vigenere Square Substitution Cipher Task Sheet for directions to how this cipher (and applet) works.