Passwords and Authentication
Strong passwords and two-factor authentication protect accounts.
About this topic
Authentication is proving who you are to a system, and passwords are the most common method. A strong password is long, unpredictable and unique to each account. Length matters most: each extra character multiplies the number of guesses needed, and a passphrase of several random words is both strong and memorable.
Good systems never store passwords in plain text. They store a hash, a one-way scrambled value, often with a random salt added so identical passwords have different hashes. When you log in, the system hashes what you type and compares. Attackers use brute force, dictionary lists of common passwords and leaked data. Authentication factors include something you know (password), something you have (phone or key) and something you are (fingerprint). Multi-factor authentication combines two or more, so a stolen password alone is not enough.
A common misconception is that replacing letters with symbols, like p@ssw0rd, makes a weak password strong; attackers know these tricks. Another is reusing passwords, so one breach exposes many accounts. Use a password manager to create and store unique passwords, and turn on multi-factor authentication wherever possible.
Key ideas
- Long and unique passwords
- Password managers
- 2FA adds a second proof
Quick check
Use cases: where Passwords and Authentication helps
- Homework: review the key idea behind Passwords and Authentication before you start a problem set.
- Exam revision: use the quick check to test whether you can recall Passwords and Authentication without notes.
- Visual learning: play with the interactive lab to see how Passwords and Authentication changes when you adjust its inputs.
- Teaching a friend: explain Passwords and Authentication in your own words, then compare your version with the key ideas.
Computing ideas run phones, search engines, games and the wider internet.
Frequently asked questions
What is Passwords and Authentication?
Strong passwords and two-factor authentication protect accounts.
What will I learn in Passwords and Authentication?
Long and unique passwords. Password managers. 2FA adds a second proof.
Is Passwords and Authentication part of Computer Science?
Yes. It is one of 80 Computer Science topics on LearnViz HighSchoolEdu, with 3 key ideas, a live animation and a quick check.
Does the Passwords and Authentication lab work on a phone or tablet?
Yes. The animation resizes to fit your screen and supports touch, so you can drag, tap and slide with your finger.
How should I study Passwords and Authentication?
Read the summary and key ideas first, play with the interactive lab to see the idea in motion, then answer the quick check. If you get a question wrong, go back to the key idea it tests.
Do I need an account, and is my progress saved?
No account is needed. Marking a topic as learned is saved in your own browser, so it stays on that device and is not sent to a server.