Am Sonntag, 26. März 2017, 20:00:12 CEST schrieb Krzysztof Kozlowski: Hi Krzysztof, > > 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 -- To unsubscribe from this list: send the line "unsubscribe linux-samsung-soc" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
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