Suppose that you need to share a large (e.g. 10 GB) file privately with a group of 100 users, and that a secure PKI is available so that each user has a public encryption key for RSA that can be looked up and verified through the PKI. Since the file is large and RSA encryption is slow, it is inefficient to encrypt the file 100 times, each time using the RSA key of one of the users. Describe an efficient hybrid method to encrypt the file so that you encrypt the file only once, and each of the 100 users but no one else is able to open the file