PERSONAL PROJECT

Password Strength Analyzer (Python CLI)

Password strength analyzer — entropy, regex, HaveIBeenPwned (Python CLI)

Context

Personal security-focused CLI tool: rigorously evaluates password strength without ever transmitting the password in plain text. Built to explore Python's regex engine, entropy mathematics, and privacy-preserving API design (HaveIBeenPwned k-anonymity). Runs interactively in the terminal and produces a full structured report in one pass.

Features Built

Entropy calculation: log₂(pool^length) character-pool-aware — composite 0–100 score
9 compiled regex rules: repeated chars, numeric/alphabetic sequences, keyboard walks (qwerty/azerty), embedded years
Dictionary matching against 30+ common passwords and base words
Crack-time estimation at 3 attack speeds (10k/s, 1M/s, 1B/s)
HaveIBeenPwned integration via k-anonymity: only the first 5 SHA-1 chars sent to the API — the password never leaves the machine
ANSI-colored terminal output with progress bar, per-criterion checklist and improvement suggestions

Stack & Technologies

Python 3 stdlib — re, hashlib (SHA-1), math, getpass (input masking)
Compiled regex — 6 rules (RE_REPEAT, RE_SEQ_NUM, RE_KEYBOARD...)
HIBP k-anonymity — only 5-char SHA-1 prefix sent to the API
requests (optional) — HaveIBeenPwned API call
ANSI escape codes — colored output and terminal progress bar
Zero mandatory dependencies — runs on stdlib alone

How It Works

1
Secure input
getpass.getpass() used to mask password entry in the terminal — never displayed in plain text.
2
Entropy & score
Character pool detected (lowercase, uppercase, digits, special). Entropy computed: log₂(pool^length). Composite 0–100 score with length and complexity bonuses.
3
Pattern analysis
9 compiled regex rules applied: repetitions, sequences, keyboard walks, embedded years. Each detected pattern penalizes the score.
4
HIBP check
SHA-1 hash of the password computed. Only the first 5 characters sent to the HIBP API (k-anonymity). Response analyzed for breach detection — password never revealed.
5
Terminal report
ANSI-colored output: score, progress bar, criteria checklist, crack-time estimate, targeted improvement suggestions.

Key Technical Choices

log₂(pool^length)

Entropy model

Character-pool aware

k-anonymity

HIBP privacy

Only 5 SHA-1 chars sent

9 regex rules

Pattern engine

RE_REPEAT, RE_SEQ_NUM, RE_KEYBOARD...

0–100

Score

Length, complexity, entropy bonuses + penalties

Zero required

Dependencies

stdlib only (requests optional)

Screenshots