2021-04-22 01:29:48

by Herbert Xu

[permalink] [raw]
Subject: Re: cortina/gemini: hwrng: what is its quality ?

On Wed, Apr 21, 2021 at 10:03:17PM +0200, Corentin Labbe wrote:
> hello
>
> I work on the crypto part of the cortina/gemini SL3516 SoC.
> The datasheet mention a HWRNG in its IP but really briefly:
> """
> The implementation is a 32-bit Hardware Random Number Generator that has a uniformed
> distribution between 0 and 2^32 -1. The hardware randomness is created by sampling data from
> different clock domains, and feeding it as input to the 32-bit maximum length LFSR (Linear Feedback
> Shift Register)
> """
>
> Piping its output to rngtest give:
> dd if=/dev/hwrng count=2000 bs=2048 | rngtest
> rngtest 6.11
> rngtest: starting FIPS tests...
> rngtest: entropy source drained
> rngtest: bits received from input: 32768000
> rngtest: FIPS 140-2 successes: 1191
> rngtest: FIPS 140-2 failures: 447
> rngtest: FIPS 140-2(2001-10-10) Monobit: 183
> rngtest: FIPS 140-2(2001-10-10) Poker: 116
> rngtest: FIPS 140-2(2001-10-10) Runs: 346
> 2000+0 records in
> 2000+0 records out
> rngtest: FIPS 140-2(2001-10-10) Long run: 0
> rngtest: FIPS 140-2(2001-10-10) Continuous run: 0
> rngtest: input channel speed: (min=303.606; avg=3143.352; max=9712.208)Kibits/s
> rngtest: FIPS tests speed: (min=7.104; avg=10.332; max=10.638)Mibits/s
> rngtest: Program run time: 13303224 microseconds
>
> That's a quite number of failure.
> Can the hwrng still be used with some "hwrng->quality" setting ?
> Or it is just too many failure to be used ?

If in doubt just leave it zero and the admin can override it if
necessary.

Thanks,
--
Email: Herbert Xu <[email protected]>
Home Page: http://gondor.apana.org.au/~herbert/
PGP Key: http://gondor.apana.org.au/~herbert/pubkey.txt


2021-04-22 06:53:30

by Corentin Labbe

[permalink] [raw]
Subject: Re: cortina/gemini: hwrng: what is its quality ?

Le Thu, Apr 22, 2021 at 10:14:30AM +1000, Herbert Xu a ?crit :
> On Wed, Apr 21, 2021 at 10:03:17PM +0200, Corentin Labbe wrote:
> > hello
> >
> > I work on the crypto part of the cortina/gemini SL3516 SoC.
> > The datasheet mention a HWRNG in its IP but really briefly:
> > """
> > The implementation is a 32-bit Hardware Random Number Generator that has a uniformed
> > distribution between 0 and 2^32 -1. The hardware randomness is created by sampling data from
> > different clock domains, and feeding it as input to the 32-bit maximum length LFSR (Linear Feedback
> > Shift Register)
> > """
> >
> > Piping its output to rngtest give:
> > dd if=/dev/hwrng count=2000 bs=2048 | rngtest
> > rngtest 6.11
> > rngtest: starting FIPS tests...
> > rngtest: entropy source drained
> > rngtest: bits received from input: 32768000
> > rngtest: FIPS 140-2 successes: 1191
> > rngtest: FIPS 140-2 failures: 447
> > rngtest: FIPS 140-2(2001-10-10) Monobit: 183
> > rngtest: FIPS 140-2(2001-10-10) Poker: 116
> > rngtest: FIPS 140-2(2001-10-10) Runs: 346
> > 2000+0 records in
> > 2000+0 records out
> > rngtest: FIPS 140-2(2001-10-10) Long run: 0
> > rngtest: FIPS 140-2(2001-10-10) Continuous run: 0
> > rngtest: input channel speed: (min=303.606; avg=3143.352; max=9712.208)Kibits/s
> > rngtest: FIPS tests speed: (min=7.104; avg=10.332; max=10.638)Mibits/s
> > rngtest: Program run time: 13303224 microseconds
> >
> > That's a quite number of failure.
> > Can the hwrng still be used with some "hwrng->quality" setting ?
> > Or it is just too many failure to be used ?
>
> If in doubt just leave it zero and the admin can override it if
> necessary.
>

But as an admin, what value I can set ?
If I do a rule-of-3, success rate is 73%.
So does a quality of 730 is ok ?

2021-04-22 07:22:07

by Herbert Xu

[permalink] [raw]
Subject: Re: cortina/gemini: hwrng: what is its quality ?

On Thu, Apr 22, 2021 at 08:52:23AM +0200, Corentin Labbe wrote:
>
> But as an admin, what value I can set ?
> If I do a rule-of-3, success rate is 73%.
> So does a quality of 730 is ok ?

This is not hard science, the admin can choose whatever value they
like.

Cheers,
--
Email: Herbert Xu <[email protected]r.apana.org.au>
Home Page: http://gondor.apana.org.au/~herbert/
PGP Key: http://gondor.apana.org.au/~herbert/pubkey.txt