So use row L and column A of the Vigenère square, namely L. Similarly, for the second letter of the plaintext, the second letter of the key is used; the letter at row E and column T is X. The Vigenère cipher is a method of encryption that uses a series of different "Caesar ciphers" based on the letters of a keyword. { Size = Text.length; // find out how long input string is for (i=0; i < Gamma.length; i++) (. If, for example, the keyword is "QUEENLY" and the message is "ATTACK AT DAWN", the key would be "QUEENLYATTACKATDAWN". The Vigenère cipher uses this table together with a keyword to encrypt a message. The ciphertext alphabet generated using keyword of "monoalphabetic". } If you do not know the keyword, one of the main weaknesses of a keyword substitution is that it is vulnerable to attack by frequency analysis. CipherText = CipherText + CipherAlpha; Giovan Battista Bellaso".However it is named, due to the wrong widespread belief in the nineteenth century, after the French diplomat and alchemist Blaise de Vigenère, who lived in the sixteenth century. Temp = ""; To encrypt pick a letter in the plaintext sentence and its corresponding letter in the keyword, use the keyword letter and plaintext letter as the row index and column index, and the entry at the row-column intersection is the letter in the cypher text. This article does not cite any sources. The keyed Caesar cipher is a variant of the Caesar Cipher that provides increased protection. For example, the first letter of the plaintext, A, is enciphered using the alphabet in row L, which is the first letter of the key. Vigenère Cipher: uses Caesar cipher, but Caesar key changes each letter based on keyword Vernam Cipher: binary version of Vigenère, using XOR One Time Pad: same as Vigenère/Vernam, but random key as long as plaintext Sig. I … The rest of the plaintext is enciphered in a similar fashion: The cipher uses a different alphabet from one of the rows at various points in the encryption process. To encode, you would find a letter in the top row and substitute it for the letter in the bottom row. .