Am Sonntag, 26. M?rz 2017, 20:00:12 CEST schrieb Krzysztof Kozlowski:

Hi Krzysztof,

quoted

Would it make sense to add another outer loop here to allow all of slen to
be injected into the DRNG? Note, in some cases, a user wants to add more
seed into the DRNG than the actual seed size. In this case, the DRNG acts
as a compression operation of entropy. This is used when the
entropy-to-data ratio is not 1:1. In a lot of cases, users have a seed
which has less entropy in bits per data bit.

Hi,

I do not know whether this would have any benefit on hardware. The
datasheet is not describing too much here. It is actually saying only:
1. Write SEED to each register (five in total).
2. Confirm that STATUS register says seeding done.
3. Start RNG engine.
4. Wait for engine finish (another bit in STATUS - clear it then).
5. Read the randoms.

I would guess that the hardware will ignore all previously written seeds
and use the last one. Maybe the hardware will use all of the seeds
written as you imply. It is just a guessing.

Oh my, if you are right with your first guess, this is a bad DRNG design.

Just out of curiousity: what happens if a caller invokes the seed function 
twice or more times (each time with the sufficient amount of bits)? What is 
your guess here?

Ciao
Stephan