Cryptocell Random number generator:

[Stefan B]

Hello,

I got a NRF52840 and want to use the BLE  S140. On the application I want to use the CC310 random number generator.

- The S140 specification states that S140 uses the RNG peripheral.

- The sdk_config.h (SDK v15.2 ) is configured to use the CC310 generator as backend ( NRF_CRYPTO_BACKEND_CC310_RNG_ENABLED) .

1.  Can I use the nrf_crypto libarry  functions nrf_crypto_init() ;    nrf_crypto_rng_vector_generate()   to generate random numbers  with the CC310  and use the S140 at the same time?
   
   
2. The cryptocell Random Generator API defines CRYS_RND_mode_t  but no function to set a mode ? Or did I miss it some where ?
   
   
3. What modes does the nrf_crypto lib use when CC310 is configured as backend ?
   
   
4. How can I have access to the TRNG of the CC310?
   
   
5. Is the more documention of how the known answer tests  CRYS_RND_EnterKatMode() work, respectivly how to use them ?
6. Is the TRNG  tested to be random under temperature / SEU effects?

Best regard

Stefan

[ovrebekk]

Hi Stefan

1. Yes. The SoftDevice doesn't use the CC310 peripheral, so you can use it freely in the application regardless of what the SoftDevice is doing. 

2. This appears to be a inconsistency in the library. The mode can not be changed, so this enum could be removed. 

3. The library will use the CRYS_RND_Slow mode. 

4. You can't access the TRNG directly, but if you reseede the RNG in between each sample the result is much the same. Please be aware that this will make the process quite slow and average power consumption higher. For most uses the CTR-DRBG algorithm should be sufficient. 

5. We don't have more documentation than what is available on the infocenter unfortunately. 

6. I need to investigate a bit more to give you an answer on this, you should hear back from me shortly. 

Best regards
Torbjørn

[Stefan B]

Hello Torbjørn,

thanks for your reply.

6.1 Could you get some more info in the meantime ?

Best regards

Stefan

[ovrebekk]

Hi Stefan

Sorry for the slow reply, I finally got hold of the test guys. We test the standard PVT corners (process, voltage, temperature), but we don't do any SEU testing. 

Best regards
Torbjørn