David McCullough wrote:
Jivin Jeff Garzik lays it down ...
David McCullough wrote:
Jivin Jeff Garzik lays it down ...
On Thu, Mar 24, 2005 at 02:27:08PM +1000, David McCullough wrote:
Hi all,
Here is a small patch for 2.6.11 that adds a routine:
add_true_randomness(__u32 *buf, int nwords);
so that true random number generator device drivers can add a entropy
to the system. Drivers that use this can be found in the latest release
of ocf-linux, an asynchronous crypto implementation for linux based on
the *BSD Cryptographic Framework.
http://ocf-linux.sourceforge.net/
Adding this can dramatically improve the performance of /dev/random on
small embedded systems which do not generate much entropy.
We've already had hardware RNG support for a while now.
No kernel patching needed.
Are you talking about /dev/hw_random ? If not then sorry I didn't see it
:-(
On a lot of the small systems I work on, /dev/random is completely
unresponsive, and all the apps use /dev/random, not /dev/hw_random.
Would you suggest making /dev/random point to /dev/hw_random then ?
All the apps are supposed to use /dev/random, so that's correct.
Ok
For Hardware RNGs, userspace rngd daemon obtains entropy, checks it
(mainly checking for hardware failures), and then stuffs entropy into
the kernel random device. http://sf.net/projects/gkernel/
On the "to do" list is making rngd directly generate entropy use
'xstore' on VIA CPUs, rather than going kernel -> userland -> kernel.
Also, there are other entropy daemons floating about. I think there is
one that obtains noise from an audio device.
I had looked at hw_random, but it seemed a little platform specific (x86),
and it doesn't currently have a way for RNG providers to register themselves.
Admittedly I did not know how it's output was being used in practice.
The drivers I am working with do crypto/public key and RNG. Not all of
them can easily have the RNG support taken from the driver and plugged
into hw_random.c, since it is (in most cases) a single PCI chip with
it's own registers, initialisation and configuration, that, IMO
belongs in the driver for the particular chip.
Agreed.
Not that it isn't possible, but hw_random would start supporting a
much larger number of HW variants and I think it would get ugly.
Agreed.
It would be possible to add a "register" interface to hw_random so that
you can register other RNG's easily. This would seem reasonable.
Agreed.
I work on fairly resource constrained embedded devices a lot of the
time, so when I can avoid adding applications and reduce kernel size,
I do. Thus my motivation to add a simple API for adding entropy to
/dev/random.
We already have the facilities to add entropy, as current use of
hw_random+rngd shows.
Jeff
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