Re: Secure Password Policy?

[Brian Anderson <andersob () darton edu>]

Neil wrote:
> On 1/19/2006 3:41 PM, Sulaiman, Wilmar wrote:
>
> > Dear all,
> >
> > I noticed that "best practice" for Minimum password length policy is
> > either 6 or 8 characters. I guess SANS institute considered a weak
> > password if it is less than 8 characters.  
> >
> > I would like to know where they derived the number (6 and 8 characters).
> > Is there any documentation to backup it up why the best practice for
> > minimum password length is set to 6?
>
>
> Thus:
> possible number of passwords = possible number of characters ^ number of
> characters in password.
> and:
> time to crack = number of passwords / number of attempts per second
>
> 361 = 36/1000 = 0.036 seconds (which is faster than you can blink)
> 362 = 1296/1000 = 1.296 seconds
> 363 = 46656/1000 = 46.656 seconds
> 364 = 1679616/1000 = 1679.616 seconds (27 minutes)
> 365 = 60466176/1000 = 60466.176 seconds (16 hours)
> 366 = 2176782336/1000 = 2176782.336 seconds (25 days)
>
> So as you can see, the amount of time really spikes up by adding the
> number of digits in your password.
>
> Mind you, password crackers today are many times faster than the example
> I did above.  So, using a real numbers, security advisories have decided
> that at 8 characters, it will take someone quite some time to crack the
> password.  (And I just don't recommend 6 characters, too trivial in
> today's day and age.)

And by having accounts lock, at least temporarily, after excessive failures brute forces can be made much less 
effective.

As the risk of the access increases, increase the lock time up to permanent locking.  3 attempts an hour will make that 
6 char password work much better. ;)
36^6 = 2176782336/3 = 725594112 hrs (30233088 days)

--
*********************************
Brian L. Anderson
Darton College
Office of Information Technology
andersob () darton edu
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