Q1) A foreign navy has implemented a secure communications system in which submarine commanders transmit a single 5-letter message every day. The messages may only use capital (English) letters, and all messages are equally probable. A crypto device encrypts each message into 20 bits of ciphertext.
a. Compute the entropy of the plaintext message?
b. Compute the entropy of the ciphertext message?
c. Is this a good cryptosystem? Why or why not?