Password Entropy

README.md

Password Entropy

Calculate the entropy of a password.

Usage

const passEnt = require('passEnt');

const H = passEnt('pswd'); // 18.801758872564367

passEnt.js

const pools = [
	{ id: 'numbers', pattern: /[0-9]/, size: 10 },
	{ id: 'l_letters', pattern: /[a-z]/, size: 26 },
	{ id: 'u_letters', pattern: /[A-Z]/, size: 26 },
	{ id: 'symbols', pattern: /[^a-zA-Z0-9]/, size: 40 }
];

const getUsedPools = (password) => {
	const used = [];

	for(let index = 0; index < password.length; index++) {
		const char = password.charAt(index);
		const pool = pools.find(p => p.pattern.test(char));

		if (pool && used.findIndex(p => p.id === pool.id) === -1) {
			used.push(pool);
		}
	}

	return used;
};

const calcPoolSize = (pools) => {
	let size = 0;

	pools.forEach(pool => {
		size += pool.size;
	});

	return size;
};

const calcPoolEntropy = (pools) => {
	const size = calcPoolSize(pools);

	return Math.log2(size);
};

module.exports = (password) => {
	const pools = getUsedPools(password);
	const charEntropy = calcPoolEntropy(pools);

	return password.length * charEntropy;
};