The Vigenére Cipher Expository Paper

French diplomat and cryptographer Blaise de Vigenére (1523-1596), developed the Vigenére Cipher in 16th century France in the mid-1580s. Vigenére was on the court of Henry III of France. Vigenére developed a polyalphabetic coding system in which one letter of plain text may be encrypted as different letters rather than one plain text letter represented as one cipher text letter throughout the encoded message. Though the Vigenére Cipher was thought to be unbreakable for almost 300 years, it was Charles Babbage who first developed a method to successfully decrypt messages encrypted using the Vigenére Cipher. This fact wasn’t known until the 1900’s for two possible reasons: 1) Babbage had a habit of not completing paperwork, or 2) he wanted to protect the fact that he had broken the code so Britain could continue to decrypt messages encrypted using the Vigenére Cipher sent in the Crimean War (1853-1856). It was left to a Prussian officer, Friedrich Wilhelm Kasiski, to share a statistical method for breaking the Vigenére Cipher in 1863, which will be discussed later in this paper. The Vigenére Cipher involves using a table that entails 26 shifts of the alphabet and a key word. The encoding process involves using a plain text message and matching letters with the key word. The intersection of the column using the plain text letter and the row of the key word letter determines the cipher text letter. The following example uses the table, the key word, a key phrase MATH ROCKS and the plain text PARALLEL LINES ignoring spaces and punctuation. Notice that the intersection of the ‘P ’ column and the ‘M ’ row gives a result of ‘B’ and the intersection of the ‘A ’ column and the ‘A ’ row gives the letter ‘A ’ as the result. (It ma