• A hacker's 'dictionary' contains 900,000 passwords which have been sold to her on the dark web. She also has gained knowledge of 300,000 usernames for a particular target site. She is going to try all the possible combinations of the passwords with all of the usernames using a brute-force attack. Her computer system can test 1 thousand million (109) combinations a second. How long will it take her to check all the passwords against all the usernames? Give your answer in seconds correct to 2 significant figures.
• ii.How long will it take if the system forces a break of 5 minutes after every 3 non-successful log-in attempts? (You can assume that the system doesn't lock any user accounts during this process). Give your answer in years, using scientific notation, correct to 2 significant figures. You should take a year as being equivalent to 3.19 x 107 seconds.