[PATCH 4/4] crypto/fsl: add RNG support

[Michael Walle]

Am 2020-06-04 14:58, schrieb Heinrich Schuchardt:
> On 04.06.20 14:52, Michael Walle wrote:
>> Am 2020-06-04 14:26, schrieb Heinrich Schuchardt:
>>> On 04.06.20 10:05, Horia Geantă wrote:
>>>> On 6/4/2020 5:31 AM, Heinrich Schuchardt wrote:
>> 
>>>> From what I see, driver added by Michael is using the PRNG / DRBG
>>>> and not the TRNG. Is this acceptable?
>>>> 
>>> 
>>> If it is only PRNG, this is not what we look for. If a PRNG/DRBG is 
>>> used
>>> to ameliorate the raw entropy stream like Linux does for the 
>>> /dev/random
>>> device this is fine. We need something non-deterministic.
>> 
>> What do you mean by "only PRNG"?
>> 
>>>> -a PRNG / DRBG (SP800-90A compliant DRBG_Hash) - which is seeded
>>>> from the TRNG
>> 
>> So while it is a PRNG, it is non-deterministic because its seeded
>> from the TRNG.
> 
> If for every byte that your DM_RNG driver outputs at least one byte 
> from
> the TRNG is consumed, it is fine. Otherwise it is not what we are
> looking for.

And why is that? This should really be documented somewhere.

-michael