Question - seeding the hw pseudo random number generator

On 03/20/2017 02:39 PM, Stephan M?ller wrote:

Am Montag, 20. M?rz 2017, 14:28:58 CET schrieb Herbert Xu:

Hi Herbert,

quoted

On Mon, Mar 20, 2017 at 12:19:32PM +0530, PrasannaKumar Muralidharan wrote:

quoted

AF_ALG interface for rng does have seeding support. I think hw_random
does not provide seeding support intentionally as I understand that
True RNG need not require seeding (please correct me if I am wrong).

Yes.  We should be converting PRNGs in hwrng over to algif_rng.

IMHO this not only applies to the PRNGs in drivers/crypto (which should simply 
register with crypto_register_rngs) but also to ~/hacking/sources/linux/arch/
s390/crypto/prng.c which exports a /dev/prandom file.

For the seeding, it may make sense to follow the example given with crypto/
drbg.c using the add_random_ready_callback function.

Ciao
Stephan

I'll have a look on it. Currently the s390/crypto/prng seeds itself with
an algorithm based on the jitter of the very fine granular hardware
clock of a s390 machine. There were some thoughts and measurements
by an mathematician which let to this algorithm. However, long-term
the s390 platform will provide some kind of true hardware random number
generator and the idea is to use this for seeding the prng.

regards
Harald Freudenberger