Password Checker

Building a Password Checker: Strength + Breach Detection in Python

I recently built my second cybersecurity tool — a password checker that does two things: analyzes password strength AND checks if it’s been leaked in a data breach. Here’s how I built it.

The Inspiration

After building my first tool (a multi-threaded port scanner), I wanted to tackle something directly related to everyday security. Passwords are everywhere, and most people don’t know if their passwords are strong or if they’ve been exposed in a breach.

I wanted to build a tool that would answer two questions:

1. Is this password strong?
2. Has this password been leaked?

What It Does

🔐 1. Strength Analysis

The tool checks five criteria and gives a score from 0-6:

Criteria Points Length (12+ characters) +2 Length (8-11 characters) +1 Uppercase letters +1 Lowercase letters +1 Numbers +1 Symbols (!@#$%^&*) +1

Score Interpretation:

Score Rating 5-6 🟢 GREAT 4 🟢 GOOD 3 🟡 DECENT 0-2 🔴 WEAK

🛡️ 2. Breach Detection

The tool checks the HaveIBeenPwned API to see if your password appears in any known data breaches.

How it stays secure:

• Your password is never sent over the internet
• Only the first 5 characters of the SHA-1 hash are sent
• This is called k-anonymity — the API never sees your full password

Conclusion
Building this password checker taught me a lot about:

Working with APIs

Cryptographic hashing

Privacy-first design

Creating useful, user-friendly tools

If you’re learning cybersecurity or Python, I highly recommend building tools like this. You learn far more than you would from following tutorials alone.

This is my second cybersecurity project. If I can build it, so can you. 🚀