nrf52833 RNG and OTP flash

[Richard R]

Hello,

Our team are evaluating the nRF52833 vs the nRF52840 and would like to understand the following

1. The nRF52840 clearly state that its RNG hardware is NIST SP800-90A and SP800-90B compliant, meanwhile the nRF52833 only mentions that it has a true-non-deterministic-RNG (section 6.19 on the Product Spec) - Is this RNG also NIST compliant?

2. Is there a space in flash for the nRF52833 where we can store keys in a One-Time-Programmable fashion (e.g. by blowing fuses to prevent re-writes) and then have that information available for computation, but read protected?

Thank you for your time!

[run_ar]

1. The nRF52840 has the cryptocell hardware which has the compliant RNG. While the nRF52833 does not have this. See CRYPTOCELL — ARM TrustZone CryptoCell 310. The RNG in the nRF52833 is not considered compliant.

2. Yes, UICR+approtect. But application flash could also be used and might be more convenient to maintain. Approtect would enable read back protection for all flash.