password/passphrase hybrid generator

randpw.pl

#!/usr/bin/perl -w

# Usage: randpw.pl <len>
# optional <len> truncate to so many chars

# using my copy of /usr/dict/words, n = 53970, so with default settings, r=2 and
# ((n+1)! / (r * (n-1)!) = 1456407435 (because its a duplicative combination at this stage)
# so there are
# (1456407435 * 1000 * 68)^3 = 9.7134 x 10^41
# possible passwords here, 
# or
# ~139 bits of entropy. Not too shabby.
# http://en.wikipedia.org/wiki/Password_strength
#
# actual output:
#   $ randpw-weak 16
#   Gripped + Unnerving
#   vUnnerving581Gripped
#   Unnerving581Grip
#
# Author: sbeam
# License: DWTFYW

my $dict = "/usr/share/dict/words";

my $maxlen = shift @ARGV;
my $wordmin = 2;
my $wordmax = 9;
my $num_words = 2;
my $skip_possessives = 1; # db contains 's forms for every noun

use List::Util qw(shuffle);

srand; 

open(WORDS, $dict) or die($!);

# two random words from dict
my $shorts = 0;
my @parts;
while (<WORDS>) {
    chop;
    next if (/'s$/ && $skip_possessives);
    if (length() >= $wordmin and length() <= $wordmax) {
        $shorts++;
        for ($i=0; $i<$num_words; $i++) {
            (rand($shorts) < 1) && ($parts[$i] = ((rand(2)<1)? ucfirst($_) : $_) );
        }
    }
}
print join(' + ', @parts) . "\n";

# a random number 0 - 1000
push(@parts, sprintf('%d', rand(1000)));

# one of these thingys, for extra l33tness
my @chars=('a'..'z','A'..'Z','0'..'9','_','-','/','+','$','@');
push(@parts, $chars[rand @chars]);

# stir and serve chilled.
my $whole = join('', shuffle @parts);
print "$whole\n";

if ($maxlen && $maxlen < length($whole)) {
    $whole = substr($whole, rand(length($whole)-$maxlen), $maxlen);
    print "$whole\n";
}