Strong passwords: how long to guess?
A computer tries a million passwords every second. Make a password longer, add letters and symbols, and see how long it would take the computer to try them all.
Core concept
A password is safer when it is long and mixes letters, digits and symbols, because the number of possible passwords to try grows enormously
Topic: Digital safety
A password keeps other people out of your phone, email and games. Someone trying to break in can use a computer to guess passwords, one after another, very fast: a million guesses every second. Is your password safe? It depends on how many possible passwords there are to try. A 4-digit PIN has only 10 × 10 × 10 × 10 = 10000 possibilities. Every extra character multiplies the number again, and using small letters (26), letters and digits (62) or letters, digits and symbols (94) multiplies it by much more each time. In this lab you build passwords and see how long the computer would need.
What you will learn
- Work out how many passwords are possible for a given length and set of characters.
- Explain why longer passwords are much harder to guess.
- Explain why mixing letters, digits and symbols makes a password stronger.
- Follow good habits for keeping passwords safe.
Before you start
- Multiply numbers and understand very large numbers.
Materials
- Paper and a pencil (never write your real password down for others to see)
Equipment
- A calculator
Procedure
- Record a 4-digit PIN.
- Record a 6-digit PIN.
- Record an 8-letter password of small letters, then one of letters and digits.
- Record a 12-character password with letters, digits and symbols.
How this simulation is simplified
- The computer tries one million (1000000) passwords every second, and must try every possible password to be sure.
- Digits give 10 characters, small letters 26, small and capital letters with digits 62, and those with symbols 94.
- A year has 365 days.