Generate passphrase randomly, but memorably

randomwords.py

#! /usr/bin/env python

"""Generate a sequence of random words for use in a password/passphrase

On my Mac, the `words` file referenced in the script has 235886 (roughly 2**18)
entries.  If you select N of those words randomly, you get roughly 18*N bits of
entropy for a password.

I like to generate a list about 10 words long, then choose about 6 of them to
form a sentence -- a ridiculous sentence, but still a sentence.  You might have
to learn some new words, and conjugate verbs, etc.  This makes it easy to
remember, but still impractical to guess.  Use capitalization, spaces between
words, and relevant punctuation -- or not -- for another few bits of entropy,
and to ease memorization if you see fit.

See also <https://xkcd.com/936/>, though he apparently assumes a dictionary of
about 2000 words, and a password of 4 words; the dictionary used here is far
stronger.  Bonus points for translating each word into another random language,
which has the effect of multiplying the number of bits by the number of random
languages.

This, of course, is good for your important passphrases; for online passwords,
use a password manager, like LastPass or Password Safe.

"""

import random

word_file = "/usr/share/dict/words"

words = open(word_file).read().splitlines()

for i in range(10):
    print(random.choice(words))