hwrng: airoha set rng quality to 900

[PATCH] hwrng: airoha set rng quality to 900

Posted by Aleksander Jan Bajkowski 1 month ago

Airoha uses RAW mode to collect noise from the TRNG. These appear to
be unprocessed oscillations from the tero loop. For this reason, they
do not have a perfect distribution and entropy. Simple noise compression
reduces its size by 9%, so setting the quality to 900 seems reasonable.
The same value is used by the downstream driver.

Compare the size before and after compression:
$ ls -l random_airoha*
-rw-r--r-- 1 aleksander aleksander 76546048 Jan  3 23:43 random_airoha
-rw-rw-r-- 1 aleksander aleksander 69783562 Jan  5 20:23 random_airoha.zip

FIPS test results:
$ cat random_airoha | rngtest -c 10000
rngtest 2.6
Copyright (c) 2004 by Henrique de Moraes Holschuh
This is free software; see the source for copying conditions.  There is NO
warranty; not even for MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.

rngtest: starting FIPS tests...
rngtest: bits received from input: 200000032
rngtest: FIPS 140-2 successes: 0
rngtest: FIPS 140-2 failures: 10000
rngtest: FIPS 140-2(2001-10-10) Monobit: 9957
rngtest: FIPS 140-2(2001-10-10) Poker: 10000
rngtest: FIPS 140-2(2001-10-10) Runs: 10000
rngtest: FIPS 140-2(2001-10-10) Long run: 4249
rngtest: FIPS 140-2(2001-10-10) Continuous run: 0
rngtest: input channel speed: (min=953.674; avg=27698.935; max=19073.486)Mibits/s
rngtest: FIPS tests speed: (min=59.791; avg=298.028; max=328.853)Mibits/s
rngtest: Program run time: 647638 microseconds

In general, these data look like real noise, but with lower entropy
than expected.

Fixes: e53ca8efcc5e ("hwrng: airoha - add support for Airoha EN7581 TRNG")
Suggested-by: Benjamin Larsson <benjamin.larsson@genexis.eu>
Signed-off-by: Aleksander Jan Bajkowski <olek2@wp.pl>
---
 drivers/char/hw_random/airoha-trng.c | 1 +
 1 file changed, 1 insertion(+)

diff --git a/drivers/char/hw_random/airoha-trng.c b/drivers/char/hw_random/airoha-trng.c
index 1dbfa9505c21..9a648f6d9fd4 100644
--- a/drivers/char/hw_random/airoha-trng.c
+++ b/drivers/char/hw_random/airoha-trng.c
@@ -212,6 +212,7 @@ static int airoha_trng_probe(struct platform_device *pdev)
 	trng->rng.init = airoha_trng_init;
 	trng->rng.cleanup = airoha_trng_cleanup;
 	trng->rng.read = airoha_trng_read;
+	trng->rng.quality = 900;
 
 	ret = devm_hwrng_register(dev, &trng->rng);
 	if (ret) {
-- 
2.47.3

Re: [PATCH] hwrng: airoha set rng quality to 900

Posted by Herbert Xu 2 weeks ago

On Mon, Jan 05, 2026 at 09:41:49PM +0100, Aleksander Jan Bajkowski wrote:
> Airoha uses RAW mode to collect noise from the TRNG. These appear to
> be unprocessed oscillations from the tero loop. For this reason, they
> do not have a perfect distribution and entropy. Simple noise compression
> reduces its size by 9%, so setting the quality to 900 seems reasonable.
> The same value is used by the downstream driver.
> 
> Compare the size before and after compression:
> $ ls -l random_airoha*
> -rw-r--r-- 1 aleksander aleksander 76546048 Jan  3 23:43 random_airoha
> -rw-rw-r-- 1 aleksander aleksander 69783562 Jan  5 20:23 random_airoha.zip
> 
> FIPS test results:
> $ cat random_airoha | rngtest -c 10000
> rngtest 2.6
> Copyright (c) 2004 by Henrique de Moraes Holschuh
> This is free software; see the source for copying conditions.  There is NO
> warranty; not even for MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.
> 
> rngtest: starting FIPS tests...
> rngtest: bits received from input: 200000032
> rngtest: FIPS 140-2 successes: 0
> rngtest: FIPS 140-2 failures: 10000
> rngtest: FIPS 140-2(2001-10-10) Monobit: 9957
> rngtest: FIPS 140-2(2001-10-10) Poker: 10000
> rngtest: FIPS 140-2(2001-10-10) Runs: 10000
> rngtest: FIPS 140-2(2001-10-10) Long run: 4249
> rngtest: FIPS 140-2(2001-10-10) Continuous run: 0
> rngtest: input channel speed: (min=953.674; avg=27698.935; max=19073.486)Mibits/s
> rngtest: FIPS tests speed: (min=59.791; avg=298.028; max=328.853)Mibits/s
> rngtest: Program run time: 647638 microseconds
> 
> In general, these data look like real noise, but with lower entropy
> than expected.
> 
> Fixes: e53ca8efcc5e ("hwrng: airoha - add support for Airoha EN7581 TRNG")
> Suggested-by: Benjamin Larsson <benjamin.larsson@genexis.eu>
> Signed-off-by: Aleksander Jan Bajkowski <olek2@wp.pl>
> ---
>  drivers/char/hw_random/airoha-trng.c | 1 +
>  1 file changed, 1 insertion(+)

Patch applied.  Thanks.
-- 
Email: Herbert Xu <herbert@gondor.apana.org.au>
Home Page: http://gondor.apana.org.au/~herbert/
PGP Key: http://gondor.apana.org.au/~herbert/pubkey.txt