Cryptography Question

This problem explores the use of a one-time pad version of the Vigenere cipher. In this scheme, the key is a stream of random numbers between 0 and 25. 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.

a. Encrypt the plaintext sendmoremoney with the key stream 9 0 1 7 23 15 21 14 11 11 2 8 9

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

c. Can a brute-force attacker (without the key) decrypt the ciphertext from part (a) in a deterministic manner?