Problem with /dev/random?
Vladimir G. Ivanovic
vladimir at acm.org
Thu May 13 21:26:08 UTC 2004
Kent,
Thanks for responding.
I am not logged in remotely but locally. I've had a "cat /dev/random"
running in a GNOME Terminal tab (window) now for several hours while I
read mail & surfed. It has printed nothing out. It has never printed
anything out, even at the very beginning.
I also moved the mouse for a good thirty seconds. Nothing.
So it appears to me that something else is wrong or improperly set up.
What happens when you cat /dev/random? Do you get some stuff out and
then periodicly as more entropy becomes available?
--- Vladimir
P.S. I thought I remembered reading that network traffic was added to
the entropy pool. Since I am listening to Internet radio, there are
always packets coming in.
------------------------------------------------------------------------
Vladimir G. Ivanovic http://leonora.org/~vladimir
2770 Cowper St. vladimir at acm.org
Palo Alto, CA 94306-2447 +1 650 678 8014
------------------------------------------------------------------------
>>>>> "kb" == Kent Borg <kentborg at borg.org> writes:
kb>
kb> On Thu, May 13, 2004 at 11:54:48AM -0700, Vladimir G. Ivanovic wrote:
>> Well, I did as suggested. Nothing. 'cat' hangs:
>>
>> open("/dev/random", O_RDONLY|O_LARGEFILE) = 3
>> fstat64(3, {st_mode=S_IFCHR|0644, st_rdev=makedev(1, 8), ...}) = 0
>> read(3,
>>
>> and never writes anything to the screen.
>>
>> How do I get GnuPG to generate keys? Do I have a problem with
>> /dev/random? (/dev/urandom seems to work. It spits out garbage
>> continuously when cat'ed.)
kb>
kb>
kb> I can maybe help a little here.
kb>
kb> /dev/random pulls random numbers from the kernel's entropy pool, and
kb> if the kernel estimates that there is not enough entropy, it blocks
kb> until there is enough entropy. /dev/urandom also produces random
kb> numbers but it doesn't block when the entropy estimation runs out.
kb> Normally /dev/urandom is about as good as /dev/random, but NOT in your
kb> case, because you seem to have no source of entropy.
kb>
kb> The easiest and least controversial source of entropy for most
kb> computers is the timing of mouse mouse movement. The keyboard is also
kb> good. Less good is the timing of network packets or variation in disk
kb> activity timings. Keyboards and mice usually default to producing
kb> entropy, I don't think other sources do.
kb>
kb> In your case you seem to have no sources of entropy. Are you logged
kb> in remotely? (If so, can someone wiggle the mouse?)
kb>
kb> Off the top of my head, I don't know what you should do next. I think
kb> there is a way to enable entropy collection for a given device on a
kb> live machine, but I don't remember how.
kb>
kb>
kb>
kb> A related issue: On shutdown the system saves the entropy pool to
kb> disk, and on startup it restores the entropy pool from disk. This
kb> means the very first time a new install boots, there is no entropy
kb> until some hgas had a chance to build up from someplace. At least in
kb> RH 9 the system also creates some keys on the first boot--at a point
kb> when there is no entropy! (I forget which keys, I know I created
kb> fresh ones on my box once I discovered that.) Does Fedora have this
kb> bug too?
kb>
kb>
kb> -kb
kb>
kb>
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kb>
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