Computer Exercise 1

(define (decrypt encrypted-message key-system)
  (let ((x (key-system-x key-system))
        (p (key-system-p key-system))
        (y-hat (encrypted-message-y encrypted-message)))
    (let ((K (expmod y-hat x p)))
      (symmetric-decrypt (encrypted-message-cipher-text encrypted-message)
			 K))))

(decrypt enc-message-ex-1 ks-ex-1)

;Value: "We don't need no education, we don't need no thought control. 
Dark sarcasm in the classroom, teacher leave those kids alone."