Q8: We know that a symmetric key encryption is simple and ecient, however, communicating parties need to share a key before using the encryption; while public key encryption is much more exible, but with a higher computational cost. Can we design a method that enjoy the best of both? For example, a public key encryption on 1k data might use less than one second, but on 5 gigabytes data, it might take two hours; on the other hand, a symmetric key encryption on 5 gigabytes still cost only a couple of, say 10 seconds. Consider the following application scenario: there are many channels in Youtube, some of which is for movie subscription. Say you are a small producer, and would like to put your movie (5 gigabytes) to Youtube. For copyright reasons you would like to send in an encrypted form. Assuming Youtubes public key pkY can be retrieved by everyone, but they do not interact with each individual user except receiving upload directly. Describe a possible protocol that enables the producer to send one round of messages to Youtube for the 5 gigabytes movie, taking about only 12 seconds?