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

[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.

Best regards

Heinrich