Deterministic test vector-based tests of ECDSA with CC310

[DamianV]

Hi,

we use CC310 (in nRF52840) in a project (working directly with the CRYS API from SDK 15.2.0). When doing a test of ECDSA with secp256r1, following the one given within the SDK (Load keys->Sign->Verify), everything works well. However, we would also like to perform deterministic tests, where we can choose all the inputs into the signing algorithm (including the one that is normally sampled with the RNG) and compare the output to a known result.

We tried to do this by feeding a dummy RNG_Function to the ECDSA signing algorithm, which outputs the desired "random data". However, the output signature does not correspond to the known result.

Is there any other way of doing the known-result tests for ECDSA signatures, and ECC key generation algorithm? How is the output of the RNG function processed by the ECDSA signing function?

[Einar Thorsrud]

Hi,

Testing key generation is not straightforward. The random number may be modified internally in the CC310 runtime library if the generated number is of bad quality, folliwing the specification in FIPS 186-4: B.1.2, B.4.2 etc. (If this is the case I expect you should see there are additional calls to the dummy RNG function you provided).

[DamianV]

Hi Einar,

thanks for your reply.

> "The random number may be modified internally in the CC310 runtime library if the generated number is of bad quality"

Does this mean, that the runtime library can further modify the output of the RNG_GenerateVector function? Is there no test mode for the RNG?