The Vigenère cipher is a method of encrypting alphabetic text by using a series of different Caesar ciphers based on the letters of a keyword. It is a simple form of polyalphabetic substitution.
Each letter of the alphabet represents a shift. For example, A = 0 (no shift), B = 1 (shift 1 to the right), C = 2 (shift 2 to the right), D = 3 (shift 3 to the right), E = 4 (shift 4 to the right), ...
If the keyword is 'BED', it means you shift the first letter of your cipher by B = 1, the second letter of the cipher by E = 4, third letter by D = 3. Repeat this pattern.
Notice how 'T' in the plaintext is represented by different letters in the cipher.
© Brian Veitch - 2013. All rights reserved.