a.The Green and Golden Gardeners club in Milton Keynes has a website for club members. The club sends out news items and seasonal hints and members are allowed to contribute. Members receive a discount from subscription fees if they contribute star articles. Members sign their articles using their own private key. Alicia Keyton is a new member.

Explain how one or more of authentication, hashing and/or types of encryption are used to ensure each of the following:

1. Only club members can log on to the website using a user name and password.

2. The club website editor can verify that an article on how to grow sweet peas is from Alicia Keyton (and not a hacker, Sam).

b.What is the maximum amount of time that it would take a computer that can test keys per second to carry out a brute-force attack on a file encrypted using 256-bit AES? Give your answer in seconds and years, using scientific notation, correct to 2 significant figures. You may assume a year is seconds and you may use a calculator to help work out the answer. Show all your working clearly in a way that will help understand how you arrived at your answer. (7 marks)