3.19 Using the Vigenre cipher, encrypt the word explanation using the key leg.

3.20 This problem explores the use of a one-time pad version of the Vigenre cipher. In this scheme, the key is a stream of random numbers between 0 and 26. For example, if the key is 3 19 5 . . . , then the first letter of plaintext is encrypted with a shift of 3 letters, the second with a shift of 19 letters, the third with a shift of 5 letters, and so on.

Encrypt the plaintext sendmoremoney with the key stream

9 0 1 7 23 15 21 14 11 11 2 8 9 

Using the ciphertext produced in part (a), find a key so that the cipher text decrypts to the plaintext cashnotneeded.