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Re: shred or scrub

Cross-posted to 2 groups.

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crankypuss <crankypuss@nomail.invalid> writes:
> On 04/19/2014 04:05 PM, Rainer Weikusat wrote:
>> "Bill Cunningham" <nospam@nspam.invalid> writes:
>>> crankypuss wrote:
>>>
>>>> There exist pseudo-devices 'zero', 'random', and 'urandom':
>>>> http://en.wikipedia.org/wiki/Device_file#Pseudo-devices
>>>
>>>      What's the difference in urandom and random devices?
>>
>> The kernel is supposed to collect 'bits with unpredictable values' from
>> 'suitable sources' and the random-device will only return such bits,
>> blocking a reader in case the already collected ones have all been
>> handed out. /dev/urandom is a hash-based PRNG which generates bits as
>> required by performing a set of calculations on the existing
>> 'unpredictable value bit pool'.

[...]

> Given that "environmental static" occurs every
> time an interaction with the network occurs,

NIC drivers don't feed input into the entropy pool (or don't do so
anymore) because 'interactions with the network' happen in response to
'interactions with the network' on some unrelated computer.

> every time some devices
> are heard from, in the elapsed time since the last request for a
> random number was received on a multi-thread system, the whole idea of
> having /dev/random block seems pretty silly.  Reducing any
> multi-thread operating system in which device events occur
> asynchronously to a state of complete cyclic stability is so insanely
> difficult as to approach impossible.

I don't quite understand what you're up to. Obviously, the number of
bits added to the entropy pool during any given time interval must be
finite, hence, it is at least theoretically possible to remove bit from
it at a higher speed and hence, exhaust the available supply sooner or
later. Considering that 'reading data from /dev/random' essentially
amounts to a memory-to-memory copy which can be done faster than
'exchanging data with some device', it doesn't seem inconceivably to
achieve this. Practically, dd can be used to test that it actually
happens: Executing

dd if=/dev/random bs=4096 count=1 of=x

on the machine I'm using to write this (3.2.9) usually results in a
couple of 'short reads' followed by an invocation which blocks for some
seconds.

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shred or scrub "Bill Cunningham" <nospam@nspam.invalid> - 2014-04-16 18:17 -0400
  Re: shred or scrub crankypuss <crankypuss@nomail.invalid> - 2014-04-17 04:19 -0600
    Re: shred or scrub "Bill Cunningham" <nospam@nspam.invalid> - 2014-04-18 22:30 -0400
      Re: shred or scrub Jasen Betts <jasen@xnet.co.nz> - 2014-04-19 07:42 +0000
        Re: shred or scrub Richard Kettlewell <rjk@greenend.org.uk> - 2014-04-19 10:04 +0100
      Re: shred or scrub crankypuss <crankypuss@nomail.invalid> - 2014-04-19 02:15 -0600
      Re: shred or scrub Rainer Weikusat <rweikusat@mobileactivedefense.com> - 2014-04-19 23:05 +0100
        Re: shred or scrub crankypuss <crankypuss@nomail.invalid> - 2014-04-20 02:47 -0600
          Re: shred or scrub John Hasler <jhasler@newsguy.com> - 2014-04-20 07:56 -0500
            Re: shred or scrub crankypuss <crankypuss@nomail.invalid> - 2014-04-21 03:51 -0600
              Re: shred or scrub Jasen Betts <jasen@xnet.co.nz> - 2014-04-21 11:50 +0000
                Re: shred or scrub crankypuss <crankypuss@nomail.invalid> - 2014-04-21 06:14 -0600
            Re: shred or scrub "Bill Cunningham" <nospam@nspam.invalid> - 2014-04-21 18:44 -0400
          Re: shred or scrub Rainer Weikusat <rweikusat@mobileactivedefense.com> - 2014-04-21 13:24 +0100
            Re: shred or scrub crankypuss <crankypuss@nomail.invalid> - 2014-04-22 04:10 -0600
              Re: shred or scrub Rainer Weikusat <rweikusat@mobileactivedefense.com> - 2014-04-22 14:39 +0100
  Re: shred or scrub Kristof Provost <kristof@codepro.be> - 2014-04-17 13:15 +0000
    Re: shred or scrub John Hasler <jhasler@newsguy.com> - 2014-04-17 09:40 -0500
      Re: shred or scrub Kristof Provost <kristof@codepro.be> - 2014-04-18 14:40 +0000
    Re: shred or scrub crankypuss <crankypuss@nomail.invalid> - 2014-04-18 02:12 -0600
      Re: shred or scrub David Brown <david.brown@hesbynett.no> - 2014-04-18 11:49 +0200
        Re: shred or scrub crankypuss <crankypuss@nomail.invalid> - 2014-04-18 09:59 -0600
          Re: shred or scrub David Brown <david.brown@hesbynett.no> - 2014-04-21 16:14 +0200
            Re: shred or scrub crankypuss <crankypuss@nomail.invalid> - 2014-04-22 04:22 -0600
              Re: shred or scrub David Brown <david.brown@hesbynett.no> - 2014-04-23 00:06 +0200
                Re: shred or scrub crankypuss <crankypuss@nomail.invalid> - 2014-04-23 05:50 -0600
                Re: shred or scrub David Brown <david.brown@hesbynett.no> - 2014-04-24 22:46 +0200
                Re: shred or scrub crankypuss <crankypuss@nomail.invalid> - 2014-04-25 03:57 -0600
                Re: shred or scrub Rainer Weikusat <rweikusat@mobileactivedefense.com> - 2014-04-25 19:14 +0100
                Re: shred or scrub crankypuss <crankypuss@nomail.invalid> - 2014-04-26 04:02 -0600
                Re: shred or scrub Rainer Weikusat <rweikusat@mobileactivedefense.com> - 2014-04-27 21:26 +0100
                Re: shred or scrub crankypuss <crankypuss@nomail.invalid> - 2014-04-28 03:27 -0600
                Re: shred or scrub Rainer Weikusat <rweikusat@mobileactivedefense.com> - 2014-04-28 12:17 +0100
                Re: shred or scrub Rainer Weikusat <rweikusat@mobileactivedefense.com> - 2014-04-28 13:01 +0100
                Re: shred or scrub crankypuss <crankypuss@nomail.invalid> - 2014-04-29 02:50 -0600
                UNIX(*)/ Linux history & system design (was: shred or scrub) Rainer Weikusat <rweikusat@mobileactivedefense.com> - 2014-05-05 21:31 +0100
                Re: UNIX(*)/ Linux history & system design crankypuss <crankypuss@nomail.invalid> - 2014-05-05 16:02 -0600
                Re: UNIX(*)/ Linux history & system design David Brown <david.brown@hesbynett.no> - 2014-05-06 01:17 +0200
                Re: UNIX(*)/ Linux history & system design crankypuss <crankypuss@nomail.invalid> - 2014-05-06 01:46 -0600
                Re: UNIX(*)/ Linux history & system design Rainer Weikusat <rweikusat@mobileactivedefense.com> - 2014-05-06 15:09 +0100
                Re: UNIX(*)/ Linux history & system design crankypuss <crankypuss@nomail.invalid> - 2014-05-06 23:47 -0600
                Re: UNIX(*)/ Linux history & system design Rainer Weikusat <rweikusat@mobileactivedefense.com> - 2014-05-07 16:23 +0100
                Re: UNIX(*)/ Linux history & system design crankypuss <crankypuss@nomail.invalid> - 2014-05-07 10:51 -0600
                Re: UNIX(*)/ Linux history & system design Jerry Peters <jerry@example.invalid> - 2014-05-07 20:25 +0000
                Re: UNIX(*)/ Linux history & system design crankypuss <crankypuss@nomail.invalid> - 2014-05-08 03:50 -0600
                Re: UNIX(*)/ Linux history & system design Jerry Peters <jerry@example.invalid> - 2014-05-08 20:24 +0000
                Re: UNIX(*)/ Linux history & system design crankypuss <crankypuss@nomail.invalid> - 2014-05-09 02:23 -0600
                Re: UNIX(*)/ Linux history & system design Rainer Weikusat <rweikusat@mobileactivedefense.com> - 2014-05-09 18:36 +0100
                Re: UNIX(*)/ Linux history & system design Rainer Weikusat <rweikusat@mobileactivedefense.com> - 2014-05-09 21:24 +0100
                Re: UNIX(*)/ Linux history & system design Rainer Weikusat <rweikusat@mobileactivedefense.com> - 2014-05-07 22:01 +0100
                Re: UNIX(*)/ Linux history & system design crankypuss <crankypuss@nomail.invalid> - 2014-05-08 03:37 -0600
                Re: UNIX(*)/ Linux history & system design Rainer Weikusat <rweikusat@mobileactivedefense.com> - 2014-05-08 14:02 +0100
                Re: UNIX(*)/ Linux history & system design crankypuss <crankypuss@nomail.invalid> - 2014-05-09 02:56 -0600
                Re: UNIX(*)/ Linux history & system design David Brown <david.brown@hesbynett.no> - 2014-05-07 00:15 +0200
                Re: UNIX(*)/ Linux history & system design crankypuss <crankypuss@nomail.invalid> - 2014-05-07 00:32 -0600
                Re: UNIX(*)/ Linux history & system design Jorgen Grahn <grahn+nntp@snipabacken.se> - 2014-05-07 08:47 +0000
                Re: UNIX(*)/ Linux history & system design crankypuss <crankypuss@nomail.invalid> - 2014-05-07 10:59 -0600
                Re: UNIX(*)/ Linux history & system design Rainer Weikusat <rweikusat@mobileactivedefense.com> - 2014-05-06 14:35 +0100
                Re: shred or scrub David Brown <david.brown@hesbynett.no> - 2014-04-26 16:30 +0200
                Re: shred or scrub crankypuss <crankypuss@nomail.invalid> - 2014-04-27 05:59 -0600
                Re: shred or scrub Rainer Weikusat <rweikusat@mobileactivedefense.com> - 2014-04-27 20:15 +0100
                Re: shred or scrub crankypuss <crankypuss@nomail.invalid> - 2014-04-28 03:29 -0600
                Re: shred or scrub Rainer Weikusat <rweikusat@mobileactivedefense.com> - 2014-04-28 12:06 +0100
                Re: shred or scrub David Brown <david.brown@hesbynett.no> - 2014-04-27 21:41 +0200
                Re: shred or scrub crankypuss <crankypuss@nomail.invalid> - 2014-04-28 04:03 -0600
                Re: shred or scrub Richard Kettlewell <rjk@greenend.org.uk> - 2014-04-28 16:44 +0100
                Re: shred or scrub David Brown <david.brown@hesbynett.no> - 2014-04-28 23:39 +0200
      Re: shred or scrub John Hasler <jhasler@newsguy.com> - 2014-04-18 07:37 -0500
        Re: shred or scrub crankypuss <crankypuss@nomail.invalid> - 2014-04-18 10:16 -0600
          Re: shred or scrub John Hasler <jhasler@newsguy.com> - 2014-04-18 12:01 -0500
      Re: shred or scrub Kristof Provost <kristof@codepro.be> - 2014-04-18 14:42 +0000
  Re: shred or scrub David Brown <david.brown@hesbynett.no> - 2014-04-17 16:41 +0200

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