How to Encode and Decode Using the Vigènere Cipher

SOLVED:To break a Vigenère cipher by recovering a plaintext message from the ciphertext message without having the key, the first step is to figure out the length of the key string. The second step is to figure out each character of the key string by deter- mining the corresponding shift. Exercises 21 and 22 deal with these two aspects. Once the length of the key string of a Vigènere cipher is known, explain how to determine each of its characters. Assume that the plaintext is long enough so tha