Using technology responsibly: digital footprints, net etiquette, intellectual property and licences, cyber crime and safety, malware, e-waste and the IT Act.
| PINs of n digits | 10ⁿ possible PINs: 4 digits → 10,000; each extra digit gives 10 times as many |
| Passwords | k characters to choose from, n places: kⁿ passwords; 26 small letters, 3 places → 17,576 |
| Time to try all | number of passwords ÷ tries per second: 10,000 PINs at 500 a second → 20 s |
| Character sets | digits 10; small letters 26; small and capital letters 52; letters and digits 62 |
| Strong password | long, mixing small and capital letters, digits and symbols; a different one for each account |
A phone is protected by a PIN of 4 digits. A program can try 500 PINs a second. (a) How many different PINs are there? (b) How many seconds would it take to try them all? (c) How many times longer would it take if the PIN had one more digit?
Working: 10 to the power 4; 10,000 ÷ 500; each extra digit gives 10 times as many PINs
Answer: (a) 10,000; (b) 20; (c) 10