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Re: Entropy Estimations for die and pass phrases

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On 2015-10-20 08:00:12 +0000, David Malone said:

> Jeffrey Goldberg <nobody@goldmark.org> writes:
> 
>> Also remember that Shannon entropy is designed to characterize
>> something like the average information content of a message.
> 
> I'd say that is was the average number of bits required to
> store/transmit a long sequence of words from that random source.

Yep. That's a better way of putting it. I was trying to focus
on the "average".

> I'd agree that Massey's paper was the start of something interesting
> here. There are also several interesting papers in between Massey's
> and Bonneau's paper - Plaim did some interesting thinking about it
> around 2000:
> 
> 	http://scholar.google.com/citations?user=neO-8uYAAAAJ&hl=en

That is one of those things I'm "aware of, but haven't read".

And of course another interesting paper between Massay's and
Bonneau's is


@article{malone2004guesswork,
	Author = {Malone, David and Sullivan, Wayne G},
	Journal = {IEEE Transactions on Information Theory},
	Number = {3},
	Pages = {525--526},
	Title = {Guesswork and entropy},
	Volume = {50},
	Year = {2004}}

One of the things that I am guilty of is not checking out the full
literature before tackling this problem myself. But I would like
to take this opportunity to warn others here of making the same
mistake.

How to characterize the strength of password generation schemes
or distributions is something that has been looked at by a number
of very smart people.

> 
>> Yes. I very much know that. I'm sorry if I said anything that
>> suggested otherwise. I was trying to point out that it is
>> an inappropriate measure for the strength of a password
>> generation scheme when that scheme doesn't produce a uniform
>> distribution.
> 
> Agreed!

I'm not at all surprised.

For those of you not familiar with David Malone, he knows a thing
or two about the distribution of human created passwords. He has
shown that although they might superficially appear to follow a
power-law distribution, when you do the statistics right you will
find that they don't:


@article{MaloneMaher11:CoRR,
	Author = {Malone, David and Maher, Kevin},
	Journal = {CoRR},
	Title = {Investigating the Distribution of Password Choices},
	Volume = {abs/1104.3722},
	Year = {2011}}

(Which reminds me that I really should post my analysis of the Adobe
breach, which is fully consistant with what you've said. Because
Adobe encrypted passwords without salt, we know the distribution
even if we don't know the individual passwords.)

Cheers,

-j

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Entropy Estimations for die and pass phrases  "David Eather" <eather@tpg.com.au> - 2015-10-18 12:05 +1000
  Re: Entropy Estimations for die and pass phrases Robert Wessel <robertwessel2@yahoo.com> - 2015-10-18 00:14 -0500
    Re: Entropy Estimations for die and pass phrases "David Eather" <eather@tpg.com.au> - 2015-10-18 16:40 +1000
  Re: Entropy Estimations for die and pass phrases  "David Eather" <eather@tpg.com.au> - 2015-10-18 16:41 +1000
  Re: Entropy Estimations for die and pass phrases Karl-Uwe Frank <karl.frank@freecx.co.uk> - 2015-10-18 23:22 +0200
    Re: Entropy Estimations for die and pass phrases Paulo Marques <pmarques@grupopie.com> - 2015-10-19 15:24 +0100
  Re: Entropy Estimations for die and pass phrases Jeffrey Goldberg <nobody@goldmark.org> - 2015-10-19 00:17 -0500
    Re: Entropy Estimations for die and pass phrases rpw3@rpw3.org (Rob Warnock) - 2015-10-19 12:00 +0000
      Re: Entropy Estimations for die and pass phrases Jeffrey Goldberg <nobody@goldmark.org> - 2015-10-19 14:52 -0500
        Re: Entropy Estimations for die and pass phrases David Malone <dwmalone@walton.maths.tcd.ie> - 2015-10-20 08:00 +0000
          Re: Entropy Estimations for die and pass phrases Jeffrey Goldberg <nobody@goldmark.org> - 2015-10-20 12:32 -0500

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