Year 9 · Autumn 2 · Cybersecurity

Brute force: a Python password-strength checker

What this lesson covers

Topic 17 Cybersecurity

KS3 Computing · Cybersecurity protects computers and data. Most attacks trick people or use weak systems, so good defences cover both.

Programming Networks and Digital CommunicationCambridge Lower Secondary Computing 0860

You will learn to

Calculate how many passwords are possible with the password formula: C to the power L.
Explain why making a password longer beats adding symbols.
Use the lock-out formula to show why three tries, then a wait, defeats brute force.
Write a Python password checker that scores length, digits and symbols.

Success criteria

I can work out 26⁸ with a calculator and say what it means.
I can compare the time to crack a password with and without a lock-out.
I can run my checker on three passwords and explain each score.

Key words

Say each word, then read what it means. Every one is in the glossary too.

Malware: Malicious software: viruses, worms, trojans, ransomware, spyware.
Phishing: Fake messages that trick people into giving details.
Brute force: Trying every possible password until one works.
Encryption: Scrambling data so only someone with the key can read it.
Firewall: Checks network traffic and blocks what isn't allowed.

The explanation

Read it here, or open the study page below to go one step at a time with things to try.

Why password length matters

Password	Calculation	Possibilities
4-digit PIN	10⁴	10,000
8 lower-case letters	26⁸	about 209 billion
8 of any keyboard symbol	94⁸	about 6 quadrillion
12 lower-case letters	26¹²	about 95 quadrillion

e.g.Example

A long passphrase like purple-violin-tuesday-rain beats a short messy one.

Study it

Open the study page and go one step at a time.

Topic 17 · Year 9

Cybersecurity

Cybersecurity protects computers and data. Most attacks trick people or exploit weak systems, so defences cover both.

Topic 14 · Year 9

Programming further

Real programs keep data in lists, take text apart as strings, split work into subroutines, and get tested on purpose.

The steps for this lesson

Topic 17, step 5: Password maths (How long to crack it?)
Topic 14, step 6: Validation (Why a lock-out beats brute force)

Try it

The maths

Symbols first, then the words, then the equation. Change the numbers to try your own.

Build it

Tinkercad · Advanced

Password lock

A lock that checks a password typed in the Serial Monitor, with validation checks and a lock-out after 3 wrong tries. Warm up the lights with blocks, then write the lock in C++.

Check yourself

One question at a time. The reason shows after each answer.

Saved on this device.