2. Consider a variant of the Vigenre cipher where instead of a word or short phrase, the key instead consists of a book or some other English-language text that is much longer than the message to be encrypted. Using this cipher, the key is never repeated, so our standard methods for retrieving the key length will fail. Now assume that Bob is a sleeper agent and Alice is his handler. Alice, using this cipher, has sent Bob a ciphertext that reads Y eplxiuuynlozlrshw The plaintext is known to contain the day of the week that Bob is supposed to receive the dead drop, followed by the day of the week he is supposed to flee the country. Determine which plaintext Alice sent to Bob, and explain how you reached your answer. Note. Each ciphertext character is equal to mi+ki (mod 26), where m; is the i-th character of the plaintext message and ki is the i-th character of the key. In particular, the alphabet is indexed from 0, so 'a' corresponds to 0, 'b' corresponds to 1, and so on. 2. Consider a variant of the Vigenre cipher where instead of a word or short phrase, the key instead consists of a book or some other English-language text that is much longer than the message to be encrypted. Using this cipher, the key is never repeated, so our standard methods for retrieving the key length will fail. Now assume that Bob is a sleeper agent and Alice is his handler. Alice, using this cipher, has sent Bob a ciphertext that reads Y eplxiuuynlozlrshw The plaintext is known to contain the day of the week that Bob is supposed to receive the dead drop, followed by the day of the week he is supposed to flee the country. Determine which plaintext Alice sent to Bob, and explain how you reached your answer. Note. Each ciphertext character is equal to mi+ki (mod 26), where m; is the i-th character of the plaintext message and ki is the i-th character of the key. In particular, the alphabet is indexed from 0, so 'a' corresponds to 0, 'b' corresponds to 1, and so on