The Vigenère Cipher Encryption and Decryption

Manual Algorithm of the Vigenere Tableau The Vigenère cipher uses a 26×26 table with A to Z as the row heading and column heading This table is usually referred to as the Vigenère Table In addition to the plaintext, the Vigenère cipher also requires a keyword, which is repeated so that the total length is equal to that of the plaintext. For example, suppose the plaintext is "GUSTI" and the keyword is "ARSYAD". Then, the keyword must be repeated as follows: Plaintext : GUSTI Key : ARSYA CipherText : GLKRI To decrypt, pick a letter in the ciphertext and its corresponding letter in the keyword, use the keyword letter to find the corresponding row, and the letter heading of the column that contains the ciphertext letter is the needed plaintext letter. For example, to decrypt the first letter "G" in the ciphertext, we find the corresponding letter "A" in the keyword. Then, the row of "A" is used to find the corresponding letter "G" and the column that contains G provides the plaintext letter "G" (if we see the above figures).