If we're going to brute force it, let's at least be clever :-). One assumption that cuts down the complexity immensely is that for a user password, it needs to be typed from the keyboard. That limits us to printable ASCII. According to my local ascii man page, printable ASCII starts at 32 (SPACE) and ends at 126 (~). However, one flaw in your attempt is that it assumes a password of exactly 8 characters. No more, no less. Let's see if we can fix that. What we really have here is a base-94 counting system (there are 95 characters in the range from 32 - 126). So, let's see if we can implement that. 
use strict;
use warnings;

use Math::BaseArith;

my $max_length = 8;
for(my $i = 0; $i < 95**$max_length; $i++) {
   my @base;
   if ($i) { #can't take log(0)
      @base = ("95") x (int((log $i) / (log 95))+1);
   }  
   else {
      @base = ("95") x (int((log 1) / (log 95))+1);
   }  
   
   my $num = encode($i, \@base);
   my $password = join('', map {chr($_+32)} @$num);
}

[download]
Now for the complexity analysis. Generating every string of up to length 8 with each character being chosen from a pool of 95 available will create (95**(8+1))-1 strings. By my math, that's 6634204312890624 strings...which is about 0.03% of your estimate. At a billion a second, this will take 19 years...a significant savings over 584!

P.S. I used ascii 32 - 126 because it was contiguous. I leave it as an exercise to the reader to add things like tab that can be typed in a keyboard but are not in that range. :-)

thor

Feel the white light, the light within
Be your own disciple, fan the sparks of will
For all of us waiting, your kingdom will come

Update: Changed the number base from 94 to 95, as per 5mi11er's observation. Also noted that I misplaced a decimal on the time calculations...it's a whole lot better than I thought!

In reply to Re^2: gettin back crypted password by thor
in thread gettin back crypted password by Anonymous Monk

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