Random password generator with a default entropy of 84 bits.

Random Password Generator

#!/usr/bin/env python
# -*- coding: utf-8 -*-

import os, string

def random_password(length=14):
    """
    Random password generator.

    Default generated password will have an entropy of 84 bits.

    For each character in the password, generate a random byte, reduce the
    integer value to modulo 64 and use the result as an index on the character
    pool.

    In a 64 character pool, each character will have an entropy of 6 bits.
    With a lenght of 14 characters the total entropy is 84 bits:

        log2(64) * 14 = 84 bits

    The difference between 13 and 14 characters can be several years to
    brute force.
    """

    characters = string.ascii_letters + string.digits + '+/'

    l = list()
    for x in xrange(length):
        i = ord(os.urandom(1))%len(characters)
        c = characters[i]
        l.append(c)
    return ''.join(l)

if __name__ == '__main__':
    print(random_password())