Re: fedora 20 disabling ssh by default

From	William Unruh <unruh@invalid.ca>
Newsgroups	comp.os.linux.misc
Subject	Re: fedora 20 disabling ssh by default
Date	2014-10-11 23:43 +0000
Organization	A noiseless patient Spider
Message-ID	<m1cfav$rbc$1@dont-email.me> (permalink)
References	(6 earlier) <m19s3t$148$1@speranza.aioe.org> <slrnm3h6qq.960.spamtrap42@one.localnet> <m1bnsj$eut$2@dont-email.me> <m1btfj$hu9$1@speranza.aioe.org> <rQh_v.410713$412.238858@fx30.iad>

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On 2014-10-11, Wayne <nospam@all.invalid> wrote:
> On 10/11/2014 2:38 PM, Bill Cunningham wrote:
>> "William Unruh" <unruh@invalid.ca> wrote in message 
>>>>>     Something generated by uuid would I think be pretty good. Or better 
>>>>> yet
>>>>> if you could direct something from dev/urandom as text; but I don't know 
>>>>> if
>>>>> you could do that.
>>>>>
>>>>> Bill
>>>>
>>>> This works for me:
>>>>
>>>>     head -c 16 /dev/random | base64
>>>>
>>>> That gives about 24 characters, including a couple of symbols.
>>>> For website passwords, I prefer to copy-paste the password into
>>>> the browser, so take a few over a dozen alphanumeric characters
>>>> from the above command.  In theory, /dev/random could block, but
>>>> even if it does, I could just spin the trackball mouse for a few
>>>> seconds.
>>>
>>> So why do you not use /dev/urandom? Using /dev/random is silly.
>> 
>>     I think there would be more entropy in urandom.
>> 
>> Bill
>> 
>> 
>
> No, on Linux there is one entropy pool, which you can
> view with cat /proc/sys/kernel/random/entropy_avail.

You mean, you can view the number of bytes in that pool with that
command.

If I do 
cat /dev/urandom>/tmp/u
after a few seconds I had 1/4GB of bytes in /tmp/u
and cat proc/sys/kernel/random/entropy_avail changed little. 

When I did 
cat /dev/random>/tmp/u
after a similar few seconds I had 64 bytes there, and the entropy pool
was around single digits in size the whole time. 

> The difference between the two is that if the available
> entropy falls below a threshold, /dev/random will block
> and /dev/urandom won't; it simply outputs lower-quality
> random numbers.

Well, no. "lower quality" is a pretty weird term for what it does. 
/dev/urandom is essentially a high quality prng which is continually
being reseeded with "randomness" from the various sources of randomness
that the operating system can supply. Being a prng one could call it
lower quality, or could also call it higher quality as it further
insulates the output from the biases etc that are always present in any
physical source of randomness. Noone has ever given even the faintest
clue of any "break" in the prng that is used for urandom, and the
continuous reseeding makes inverting it exceedingly difficult-- even
more difficult than the PRNG might be if it were never reseeded.

Unless you really really really know what you are doing, use urandom.

>

Thread

fedora 20 disabling ssh by default "Bill Cunningham" <nospam@nspam.invalid> - 2014-10-09 19:23 -0400
  Re: fedora 20 disabling ssh by default Bit Twister <BitTwister@mouse-potato.com> - 2014-10-09 23:35 +0000
    Re: fedora 20 disabling ssh by default Baho Utot <baho-utot@columbus.rr.com> - 2014-10-09 20:25 -0400
      Re: fedora 20 disabling ssh by default Bit Twister <BitTwister@mouse-potato.com> - 2014-10-10 01:11 +0000
      Re: fedora 20 disabling ssh by default William Unruh <unruh@invalid.ca> - 2014-10-10 15:32 +0000
        Re: fedora 20 disabling ssh by default Baho Utot <baho-utot@columbus.rr.com> - 2014-10-10 17:59 -0400
    Re: fedora 20 disabling ssh by default "Bill Cunningham" <nospam@nspam.invalid> - 2014-10-09 23:13 -0400
      Re: fedora 20 disabling ssh by default Rich <rich@example.invalid> - 2014-10-10 08:50 +0000
        Re: fedora 20 disabling ssh by default Bit Twister <BitTwister@mouse-potato.com> - 2014-10-10 09:10 +0000
          Re: fedora 20 disabling ssh by default The Natural Philosopher <tnp@invalid.invalid> - 2014-10-10 10:16 +0100
            Re: fedora 20 disabling ssh by default "Bill Cunningham" <nospam@nspam.invalid> - 2014-10-10 20:05 -0400
              Re: fedora 20 disabling ssh by default The Natural Philosopher <tnp@invalid.invalid> - 2014-10-11 07:47 +0100
          Re: fedora 20 disabling ssh by default Rich <rich@example.invalid> - 2014-10-10 09:26 +0000
            Re: fedora 20 disabling ssh by default The Natural Philosopher <tnp@invalid.invalid> - 2014-10-10 11:00 +0100
            Re: fedora 20 disabling ssh by default Bit Twister <BitTwister@mouse-potato.com> - 2014-10-10 10:14 +0000
              Re: fedora 20 disabling ssh by default Rich <rich@example.invalid> - 2014-10-10 10:29 +0000
            Re: fedora 20 disabling ssh by default "Bill Cunningham" <nospam@nspam.invalid> - 2014-10-10 16:27 -0400
          Re: fedora 20 disabling ssh by default William Unruh <unruh@invalid.ca> - 2014-10-10 15:41 +0000
            Re: fedora 20 disabling ssh by default "Bill Cunningham" <nospam@nspam.invalid> - 2014-10-10 20:03 -0400
              Re: fedora 20 disabling ssh by default John Hasler <jhasler@newsguy.com> - 2014-10-10 20:28 -0500
              Re: fedora 20 disabling ssh by default Robert Riches <spamtrap42@jacob21819.net> - 2014-10-11 02:52 +0000
                Re: fedora 20 disabling ssh by default William Unruh <unruh@invalid.ca> - 2014-10-11 17:03 +0000
                Re: fedora 20 disabling ssh by default "Bill Cunningham" <nospam@nspam.invalid> - 2014-10-11 14:38 -0400
                Re: fedora 20 disabling ssh by default Wayne <nospam@all.invalid> - 2014-10-11 18:05 -0400
                Re: fedora 20 disabling ssh by default Richard Kettlewell <rjk@greenend.org.uk> - 2014-10-11 23:18 +0100
                Re: fedora 20 disabling ssh by default William Unruh <unruh@invalid.ca> - 2014-10-11 23:43 +0000
                Re: fedora 20 disabling ssh by default Rich <rich@example.invalid> - 2014-10-11 22:34 +0000
                Re: fedora 20 disabling ssh by default Wayne <nospam@all.invalid> - 2014-10-11 19:13 -0400
                Re: fedora 20 disabling ssh by default William Unruh <unruh@invalid.ca> - 2014-10-12 00:30 +0000
                Re: fedora 20 disabling ssh by default Wayne <nospam@all.invalid> - 2014-10-11 21:27 -0400
                Re: fedora 20 disabling ssh by default William Unruh <unruh@invalid.ca> - 2014-10-12 02:14 +0000
              Re: fedora 20 disabling ssh by default Rich <rich@example.invalid> - 2014-10-11 03:59 +0000
      Re: fedora 20 disabling ssh by default William Unruh <unruh@invalid.ca> - 2014-10-10 15:34 +0000
  Re: fedora 20 disabling ssh by default William Unruh <unruh@invalid.ca> - 2014-10-10 15:31 +0000
  Re: fedora 20 disabling ssh by default Andreas Kohlbach <oct14.5.ankman@spamgourmet.com> - 2014-10-10 16:06 -0400
    Re: fedora 20 disabling ssh by default "Bill Cunningham" <nospam@nspam.invalid> - 2014-10-10 20:00 -0400
      Re: fedora 20 disabling ssh by default William Unruh <unruh@invalid.ca> - 2014-10-11 17:02 +0000
      Re: fedora 20 disabling ssh by default Andreas Kohlbach <oct14.5.ankman@spamgourmet.com> - 2014-10-11 16:35 -0400
  Re: fedora 20 disabling ssh by default HakTar <FiteWinTel@gmail.com> - 2014-10-30 07:34 +0000

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