| Message ID | 20200831140042.2049-1-m.felsch@pengutronix.de (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
| Series | hwrng: imx-rngc - add quality to use it as kernel entropy pool | expand |
On Mon, Aug 31, 2020 at 04:00:42PM +0200, Marco Felsch wrote: > The RM describes the RNGB as follow: > 8<---------------------------------------------------------------- > The RNGB uses the True Random Number Generator (TRNG) and a > Pseudo-Random Number Generator (PRNG) to achieve a true randomness and > cryptographic strength. > 8<---------------------------------------------------------------- > > The RNGB has 3 operation modes: self-test, seed-generation and the final > 'random number generation' mode. Before we can retrieve random numbers > from the RNGB we need to generate the seed pool: > 8<---------------------------------------------------------------- > During the seed generation, the RNGB adds the entropy generated in the > TRNG to the 256-bit XKEY register. The PRNG algorithm executes 20.000 > entropy samples from the TRNG to create an initial seed for the random > number generation. > 8<---------------------------------------------------------------- > > The RNGB can generate 2^20 words (1 word == 4 byte) of 'random' data > after the seed pool was initialized. The pool needs to be reseeded if > more words are required. The reseeding is done automatically since > commit 3acd9ea9331c ("hwrng: imx-rngc - use automatic seeding"). > > We can't retrieve the TRNG values directly so we need a other way to get > the quality level. We know that the PRNG uses 20.000 entropy samples > from the TRNG to generate 2^20 words (1MiB) and the quality level is > defined as (in bits of entropy per 1024 bits of input). So the quality > level can be calculated by: > > 20.000 * 1024 > ------------- = ~ 19.5 > 2^20 > > Signed-off-by: Marco Felsch <m.felsch@pengutronix.de> > --- > drivers/char/hw_random/imx-rngc.c | 1 + > 1 file changed, 1 insertion(+) Patch applied. Thanks.
diff --git a/drivers/char/hw_random/imx-rngc.c b/drivers/char/hw_random/imx-rngc.c index 9c47e431ce90..61c844baf26e 100644 --- a/drivers/char/hw_random/imx-rngc.c +++ b/drivers/char/hw_random/imx-rngc.c @@ -285,6 +285,7 @@ static int imx_rngc_probe(struct platform_device *pdev) rngc->rng.init = imx_rngc_init; rngc->rng.read = imx_rngc_read; rngc->rng.cleanup = imx_rngc_cleanup; + rngc->rng.quality = 19; rngc->dev = &pdev->dev; platform_set_drvdata(pdev, rngc);
The RM describes the RNGB as follow: 8<---------------------------------------------------------------- The RNGB uses the True Random Number Generator (TRNG) and a Pseudo-Random Number Generator (PRNG) to achieve a true randomness and cryptographic strength. 8<---------------------------------------------------------------- The RNGB has 3 operation modes: self-test, seed-generation and the final 'random number generation' mode. Before we can retrieve random numbers from the RNGB we need to generate the seed pool: 8<---------------------------------------------------------------- During the seed generation, the RNGB adds the entropy generated in the TRNG to the 256-bit XKEY register. The PRNG algorithm executes 20.000 entropy samples from the TRNG to create an initial seed for the random number generation. 8<---------------------------------------------------------------- The RNGB can generate 2^20 words (1 word == 4 byte) of 'random' data after the seed pool was initialized. The pool needs to be reseeded if more words are required. The reseeding is done automatically since commit 3acd9ea9331c ("hwrng: imx-rngc - use automatic seeding"). We can't retrieve the TRNG values directly so we need a other way to get the quality level. We know that the PRNG uses 20.000 entropy samples from the TRNG to generate 2^20 words (1MiB) and the quality level is defined as (in bits of entropy per 1024 bits of input). So the quality level can be calculated by: 20.000 * 1024 ------------- = ~ 19.5 2^20 Signed-off-by: Marco Felsch <m.felsch@pengutronix.de> --- drivers/char/hw_random/imx-rngc.c | 1 + 1 file changed, 1 insertion(+)