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Re: Password validation security issue

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On Sun, Mar 2, 2014 at 6:54 AM, Christian Heimes <christian@python.org> wrote:
> Yes, for most applications brute force is still the best option to crack
> the password. Passwords are usually rather short, have a low entropy and
> modern hardware is insanely fast. With software like [1] and a fast GPU
> it is possible to do more than 10*10^9 checks/second for SHA-256.

Using XKCD 936's estimate, 44 bits of entropy would still require
17592 seconds of processing at 10^9 per second. That's not a lot if
someone's personally targeting you *and* they know you use XKCD 936
*and* know the exact set of 2048 words that you drew your password
from *and* they know how you lay them out (spaces between, no spaces,
whether or not you capitalize the words, etc etc). Not knowing any of
these would add a few more bits of entropy; and if you use
/usr/share/dict/words and take only those words which consist entirely
of lower-case letters, then your corpus is over 65536 words [1], so
you have 64 bits of entropy. Even at 10^10 checks/second (which is
what 10*10^9 is, but that's an odd way to write it), that would be
21350 *days* of dedicated processing, just to crack the one password.
If cracking my password, and mine alone, in sixty years, is considered
"insanely fast", then I'm going to keep using SHA-256 for a while.

The problem isn't SHA-256. The problem is insecure passwords, the way
we've been taught to make them by the banks. Hence, XKCD 936.

ChrisA

[1] On my Debian Wheezy system:
$ grep -c '^[a-z]*$' /usr/share/dict/words
72861

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Thread

Password validation security issue Renato <rvernucio@gmail.com> - 2014-03-01 09:49 -0800
  Re: Password validation security issue Chris Angelico <rosuav@gmail.com> - 2014-03-02 05:11 +1100
  Re: Password validation security issue Christian Heimes <christian@python.org> - 2014-03-01 19:31 +0100
  Re: Password validation security issue Tim Chase <python.list@tim.thechases.com> - 2014-03-01 12:38 -0600
  Re: Password validation security issue Chris Angelico <rosuav@gmail.com> - 2014-03-02 05:43 +1100
  Re: Password validation security issue Chris Angelico <rosuav@gmail.com> - 2014-03-02 05:45 +1100
  Re: Password validation security issue Christian Heimes <christian@python.org> - 2014-03-01 20:54 +0100
    Re: Password validation security issue Roy Smith <roy@panix.com> - 2014-03-01 15:25 -0500
      Re: Password validation security issue Christian Heimes <christian@python.org> - 2014-03-01 23:07 +0100
      Re: Password validation security issue Chris Angelico <rosuav@gmail.com> - 2014-03-02 09:13 +1100
  Re: Password validation security issue Chris Angelico <rosuav@gmail.com> - 2014-03-02 07:11 +1100
  Re: Password validation security issue Christian Heimes <christian@python.org> - 2014-03-02 20:25 +0100
    Re: Password validation security issue Roy Smith <roy@panix.com> - 2014-03-02 15:01 -0500
      Re: Password validation security issue Chris Angelico <rosuav@gmail.com> - 2014-03-03 07:32 +1100
      Re: Password validation security issue Steven D'Aprano <steve+comp.lang.python@pearwood.info> - 2014-03-03 01:16 +0000
        Re: Password validation security issue Ian Kelly <ian.g.kelly@gmail.com> - 2014-03-02 18:52 -0700
          Re: Password validation security issue Steven D'Aprano <steve@pearwood.info> - 2014-03-03 04:38 +0000
            Re: Password validation security issue Chris Angelico <rosuav@gmail.com> - 2014-03-03 16:44 +1100
            Re: Password validation security issue Ian Kelly <ian.g.kelly@gmail.com> - 2014-03-02 23:50 -0700
        Re: Password validation security issue Chris Angelico <rosuav@gmail.com> - 2014-03-03 13:56 +1100
          Re: Password validation security issue Roy Smith <roy@panix.com> - 2014-03-03 08:41 -0500
            Re: Password validation security issue Chris Angelico <rosuav@gmail.com> - 2014-03-04 00:55 +1100
              Re: Password validation security issue Steven D'Aprano <steve+comp.lang.python@pearwood.info> - 2014-03-03 16:46 +0000
                Re: Password validation security issue Chris Angelico <rosuav@gmail.com> - 2014-03-04 05:46 +1100
            Re: Password validation security issue MRAB <python@mrabarnett.plus.com> - 2014-03-03 16:29 +0000
            Re: Password validation security issue Steven D'Aprano <steve+comp.lang.python@pearwood.info> - 2014-03-03 17:41 +0000
  Re: Password validation security issue Renato <rvernucio@gmail.com> - 2014-03-02 15:10 -0800
    Re: Password validation security issue Ian Kelly <ian.g.kelly@gmail.com> - 2014-03-02 18:49 -0700
    Re: Password validation security issue Steven D'Aprano <steve+comp.lang.python@pearwood.info> - 2014-03-03 02:30 +0000

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