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Re: One-line password generator

From Mario Castelán Castro <marioxcc.MT@yandex.com>
Newsgroups linux.debian.user
Subject Re: One-line password generator
Date 2017-08-27 04:20 +0200
Message-ID <uiVl7-18U-1@gated-at.bofh.it> (permalink)
References <uhiYz-45R-39@gated-at.bofh.it> <uiO0i-4Ek-3@gated-at.bofh.it>
Organization linux.* mail to news gateway

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On 26/08/17 13:25, Brian wrote:
> How does this
> 
>  echo 'secretpassword' | sha256sum - | base64 | cut -c -30 | head -1
> 
> compare with your recommendation?

I do not see the point in this post-processing.

It seems that you have a very wrong impression of what makes a password
generation scheme be a good password generation scheme.

For any probability distribution fixed in advanced, the *expected* (in
the sense used in probability theory) entropy of a password generated
with my scheme is well defined and at least 132 bits (I wanted 128 bits,
but using Base64 the choice is between 132 bits and 126 bits because 132
is not a multiple of 6). In other words, if you take a probability
distribution and keep if fixed while generating a big amount of
passwords with my scheme, the average entropy under that probability
distribution will be at least (within sampling error) 132 bits.

This property is achieved *because* there is a source of randomness
(that we can assume, has uniform distribution and thus maximal entropy
per byte) in my generation scheme, not because of Base64. Base64 is
there just to turn the random bytes into a *short* human-readable
string. One could turn the random bytes instead into a list of words (as
long as the mapping is one-to-one) and the same property about expected
entropy would hold, but then the password would be *much* longer.

Length is the *only* reason to use Base64 here instead of using the
random bytes to choose words at random.

By contrast, your “scheme” has no systematic source of randomness. It
requires that one has already decided for a “randompassword”, and then
post-process it. If the attacker knows the post-processing, guessing
this password is at least as easy than guessing the input to the
post-processing step (plus computing the hash and encoding, but this is
negligible). Moreover, your post-processing stage loses information, as
another user has already noted. If the attacker knows your
post-processing method, he can speed the search by avoid trying the
passwords that could not be possibly generated with your method because
of this loss of information.

For example, your method will never generate a string of '0000...'
because the input to Base64 are hex digits in ASCII, which never have
the byte value 0 (0 is unprintable).

If the attacker does not know the post-processing stage, then maybe he
will eventually begin to guess that your password is an human-generated
password ran through a post-processing stage. Then very possibly your
post-processing adds security (because the attacker has to guess the
post-processing method too), but how much? *It is not well defined*. We
already talked about non-well-defined probabilities, so I will not
repeat that fragment.

-- 
Do not eat animals, respect them as you respect people.
https://duckduckgo.com/?q=how+to+(become+OR+eat)+vegan

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One-line password generator Mario Castelán Castro <marioxcc.MT@yandex.com> - 2017-08-22 17:10 +0200
  Re: One-line password generator Brian <ad44@cityscape.co.uk> - 2017-08-22 21:50 +0200
    Re: One-line password generator <tomas@tuxteam.de> - 2017-08-22 22:10 +0200
      Re: One-line password generator John Hasler <jhasler@newsguy.com> - 2017-08-22 22:50 +0200
        Re: One-line password generator Jude DaShiell <jdashiel@panix.com> - 2017-08-23 14:40 +0200
    Re: One-line password generator Mario Castelán Castro <marioxcc.MT@yandex.com> - 2017-08-22 22:20 +0200
      Re: One-line password generator Mario Castelán Castro <marioxcc.MT@yandex.com> - 2017-08-22 22:20 +0200
      Re: One-line password generator Mario Castelán Castro <marioxcc.MT@yandex.com> - 2017-08-22 22:30 +0200
        Re: One-line password generator Glenn English <ghe2001@gmail.com> - 2017-08-23 22:40 +0200
      Re: One-line password generator Brian <ad44@cityscape.co.uk> - 2017-08-23 00:40 +0200
        Re: One-line password generator Lck Ras <likcoras@riseup.net> - 2017-08-23 02:30 +0200
          Re: One-line password generator Brian <ad44@cityscape.co.uk> - 2017-08-23 19:20 +0200
            Re: One-line password generator Lck Ras <likcoras@riseup.net> - 2017-08-24 03:00 +0200
        Re: One-line password generator Mario Castelán Castro <marioxcc.MT@yandex.com> - 2017-08-23 17:20 +0200
          Re: One-line password generator Brian <ad44@cityscape.co.uk> - 2017-08-23 19:00 +0200
            Re: One-line password generator Mario Castelán Castro <marioxcc.MT@yandex.com> - 2017-08-23 20:00 +0200
              Re: One-line password generator Brian <ad44@cityscape.co.uk> - 2017-08-23 21:20 +0200
                Re: One-line password generator Mario Castelán Castro <marioxcc.MT@yandex.com> - 2017-08-24 01:10 +0200
                Re: One-line password generator Brian <ad44@cityscape.co.uk> - 2017-08-24 19:50 +0200
                Re: One-line password generator David Wright <deblis@lionunicorn.co.uk> - 2017-08-25 03:00 +0200
                Re: One-line password generator Curt <curty@free.fr> - 2017-08-25 10:50 +0200
                Re: One-line password generator "Thomas Schmitt" <scdbackup@gmx.net> - 2017-08-25 11:30 +0200
                Re: One-line password generator Mario Castelán Castro <marioxcc.MT@yandex.com> - 2017-08-25 15:40 +0200
                Re: One-line password generator "Thomas Schmitt" <scdbackup@gmx.net> - 2017-08-25 16:50 +0200
                Re: One-line password generator Mario Castelán Castro <marioxcc.MT@yandex.com> - 2017-08-25 18:10 +0200
                Re: One-line password generator "Thomas Schmitt" <scdbackup@gmx.net> - 2017-08-25 19:20 +0200
                Re: One-line password generator Mario Castelán Castro <marioxcc.MT@yandex.com> - 2017-08-25 20:10 +0200
                Re: One-line password generator "Thomas Schmitt" <scdbackup@gmx.net> - 2017-08-25 20:50 +0200
                Re: One-line password generator Mario Castelán Castro <marioxcc.MT@yandex.com> - 2017-08-25 21:00 +0200
                Re: One-line password generator Brian <ad44@cityscape.co.uk> - 2017-08-25 19:00 +0200
                Re: One-line password generator Mario Castelán Castro <marioxcc.MT@yandex.com> - 2017-08-25 19:00 +0200
                Re: One-line password generator Mario Castelán Castro <marioxcc.MT@yandex.com> - 2017-08-25 19:20 +0200
                Re: One-line password generator Brian <ad44@cityscape.co.uk> - 2017-08-25 20:20 +0200
                Re: One-line password generator Brian <ad44@cityscape.co.uk> - 2017-08-25 19:20 +0200
    Re: One-line password generator Jape Person <japers@comcast.net> - 2017-08-22 22:20 +0200
      Re: One-line password generator Jude DaShiell <jdashiel@panix.com> - 2017-08-23 14:40 +0200
    Re: One-line password generator Mike McClain <mike.junk.46@att.net> - 2017-08-23 03:10 +0200
  Re: One-line password generator Teemu Likonen <tlikonen@iki.fi> - 2017-08-23 06:10 +0200
  Re: One-line password generator Aaron Toponce <aaron.toponce@gmail.com> - 2017-08-23 21:20 +0200
    Re: One-line password generator Greg Wooledge <wooledg@eeg.ccf.org> - 2017-08-23 21:30 +0200
      Re: One-line password generator Aaron Toponce <aaron.toponce@gmail.com> - 2017-08-23 21:40 +0200
        Re: One-line password generator Fungi4All <fungilife@protonmail.com> - 2017-08-23 22:50 +0200
          Re: One-line password generator Terence <terence.john@gmail.com> - 2017-08-23 23:40 +0200
  Re: One-line password generator Brian <ad44@cityscape.co.uk> - 2017-08-26 20:30 +0200
    Re: One-line password generator Nicolas George <george@nsup.org> - 2017-08-26 20:40 +0200
      Re: One-line password generator Brian <ad44@cityscape.co.uk> - 2017-08-26 21:10 +0200
        Re: One-line password generator Brian <ad44@cityscape.co.uk> - 2017-08-27 16:00 +0200
    Re: One-line password generator "Thomas Schmitt" <scdbackup@gmx.net> - 2017-08-26 21:20 +0200
      Re: One-line password generator Brian <ad44@cityscape.co.uk> - 2017-08-27 16:00 +0200
        Re: One-line password generator "Thomas Schmitt" <scdbackup@gmx.net> - 2017-08-27 17:10 +0200
          Re: One-line password generator Curt <curty@free.fr> - 2017-08-27 20:10 +0200
          Re: One-line password generator Brian <ad44@cityscape.co.uk> - 2017-08-27 20:10 +0200
            Re: One-line password generator "Thomas Schmitt" <scdbackup@gmx.net> - 2017-08-27 21:10 +0200
              Re: One-line password generator Andy Smith <andy@strugglers.net> - 2017-08-28 00:00 +0200
                Re: One-line password generator "Thomas Schmitt" <scdbackup@gmx.net> - 2017-08-28 09:40 +0200
                Re: One-line password generator Curt <curty@free.fr> - 2017-08-28 11:40 +0200
                Re: One-line password generator "Thomas Schmitt" <scdbackup@gmx.net> - 2017-08-28 12:10 +0200
                Re: One-line password generator Andy Smith <andy@strugglers.net> - 2017-08-28 13:50 +0200
                Re: One-line password generator "Thomas Schmitt" <scdbackup@gmx.net> - 2017-08-28 15:20 +0200
                Re: One-line password generator Zenaan Harkness <zenaan@freedbms.net> - 2017-08-29 04:40 +0200
                Re: One-line password generator "Thomas Schmitt" <scdbackup@gmx.net> - 2017-08-29 09:10 +0200
                Re: One-line password generator Zenaan Harkness <zenaan@freedbms.net> - 2017-08-29 10:50 +0200
                Re: One-line password generator Zenaan Harkness <zenaan@freedbms.net> - 2017-08-29 11:00 +0200
                Re: One-line password generator "Thomas Schmitt" <scdbackup@gmx.net> - 2017-08-29 12:50 +0200
                Re: One-line password generator Zenaan Harkness <zenaan@freedbms.net> - 2017-08-29 13:00 +0200
                Re: One-line password generator "Thomas Schmitt" <scdbackup@gmx.net> - 2017-08-29 14:30 +0200
                Re: One-line password generator Zenaan Harkness <zenaan@freedbms.net> - 2017-08-30 03:50 +0200
                Re: One-line password generator "Thomas Schmitt" <scdbackup@gmx.net> - 2017-08-30 12:40 +0200
                Re: One-line password generator Andy Smith <andy@strugglers.net> - 2017-08-29 14:10 +0200
                Re: One-line password generator "Thomas Schmitt" <scdbackup@gmx.net> - 2017-08-29 15:00 +0200
                Re: One-line password generator Zenaan Harkness <zenaan@freedbms.net> - 2017-08-30 03:50 +0200
                Re: One-line password generator Greg Wooledge <wooledg@eeg.ccf.org> - 2017-08-30 14:20 +0200
                Re: One-line password generator Gene Heskett <gheskett@shentel.net> - 2017-08-30 14:50 +0200
                Re: One-line password generator "Thomas Schmitt" <scdbackup@gmx.net> - 2017-08-30 15:20 +0200
                Re: One-line password generator Gene Heskett <gheskett@shentel.net> - 2017-08-30 15:30 +0200
                Re: One-line password generator "Thomas Schmitt" <scdbackup@gmx.net> - 2017-08-30 15:50 +0200
                Re: One-line password generator Gene Heskett <gheskett@shentel.net> - 2017-08-30 16:00 +0200
                Re: One-line password generator Greg Wooledge <wooledg@eeg.ccf.org> - 2017-08-30 16:10 +0200
                Re: One-line password generator Gene Heskett <gheskett@shentel.net> - 2017-08-30 18:50 +0200
                Re: One-line password generator "Thomas Schmitt" <scdbackup@gmx.net> - 2017-08-30 16:30 +0200
                Re: One-line password generator Gene Heskett <gheskett@shentel.net> - 2017-08-30 20:10 +0200
                Re: One-line password generator "Thomas Schmitt" <scdbackup@gmx.net> - 2017-08-30 23:00 +0200
                Re: One-line password generator "Thomas Schmitt" <scdbackup@gmx.net> - 2017-09-01 10:40 +0200
                Re: One-line password generator "Thomas Schmitt" <scdbackup@gmx.net> - 2017-09-01 10:50 +0200
                Re: One-line password generator Curt <curty@free.fr> - 2017-08-30 16:30 +0200
                Re: One-line password generator "Thomas Schmitt" <scdbackup@gmx.net> - 2017-08-30 17:00 +0200
                Re: One-line password generator Brian <ad44@cityscape.co.uk> - 2017-08-30 20:00 +0200
                Re: One-line password generator Zenaan Harkness <zenaan@freedbms.net> - 2017-08-29 11:00 +0200
            Re: One-line password generator "Thomas Schmitt" <scdbackup@gmx.net> - 2017-08-27 21:20 +0200
              Re: One-line password generator Brian <ad44@cityscape.co.uk> - 2017-08-29 21:20 +0200
                Re: One-line password generator Reco <recoverym4n@gmail.com> - 2017-08-29 21:40 +0200
                Re: One-line password generator Brian <ad44@cityscape.co.uk> - 2017-08-29 22:00 +0200
                Re: One-line password generator "Thomas Schmitt" <scdbackup@gmx.net> - 2017-08-29 23:00 +0200
                Re: One-line password generator Curt <curty@free.fr> - 2017-08-30 10:50 +0200
                Re: One-line password generator "Thomas Schmitt" <scdbackup@gmx.net> - 2017-08-30 12:40 +0200
                Re: One-line password generator Reco <recoverym4n@gmail.com> - 2017-08-30 00:00 +0200
                Re: One-line password generator Brian <ad44@cityscape.co.uk> - 2017-08-31 21:10 +0200
                Re: One-line password generator Fungi4All <fungilife@protonmail.com> - 2017-08-31 21:20 +0200
                Re: One-line password generator Reco <recoverym4n@gmail.com> - 2017-08-31 21:40 +0200
    Re: One-line password generator Mario Castelán Castro <marioxcc.MT@yandex.com> - 2017-08-27 04:20 +0200
      Re: One-line password generator Brian <ad44@cityscape.co.uk> - 2017-08-27 16:00 +0200
        Re: One-line password generator Mario Castelán Castro <marioxcc.MT@yandex.com> - 2017-08-27 16:40 +0200
  Re: One-line password generator Mario Castelán Castro <marioxcc.MT@yandex.com> - 2017-09-01 17:00 +0200
    Re: One-line password generator Brian <ad44@cityscape.co.uk> - 2017-09-01 21:50 +0200
      Re: One-line password generator "Thomas Schmitt" <scdbackup@gmx.net> - 2017-09-01 23:50 +0200
        Re: One-line password generator Jude DaShiell <jdashiel@panix.com> - 2017-09-02 11:50 +0200
          Re: One-line password generator "Thomas Schmitt" <scdbackup@gmx.net> - 2017-09-02 13:00 +0200
            Re: One-line password generator Brian <ad44@cityscape.co.uk> - 2017-09-02 19:20 +0200
              Re: One-line password generator Jude DaShiell <jdashiel@panix.com> - 2017-09-02 20:30 +0200
              Re: One-line password generator "Thomas Schmitt" <scdbackup@gmx.net> - 2017-09-02 21:00 +0200
                Re: One-line password generator Brian <ad44@cityscape.co.uk> - 2017-09-02 22:00 +0200
      Re: One-line password generator Zenaan Harkness <zenaan@freedbms.net> - 2017-09-02 01:50 +0200
    Re: One-line password generator Zenaan Harkness <zenaan@freedbms.net> - 2017-09-02 01:50 +0200
      Re: One-line password generator Mario Castelán Castro <marioxcc.MT@yandex.com> - 2017-09-02 04:40 +0200
        Re: One-line password generator Zenaan Harkness <zenaan@freedbms.net> - 2017-09-02 05:40 +0200
          Re: One-line password generator Mario Castelán Castro <marioxcc.MT@yandex.com> - 2017-09-02 16:40 +0200
            Re: One-line password generator Zenaan Harkness <zenaan@freedbms.net> - 2017-09-04 01:10 +0200

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