CC310 CRYS_ECDSA_SignUserContext_t correct use

[DamianV]

Hi,

we're developing a project on nRF52840, and need to directly use the CC310 API.

The input parameters of the function CRYS_ECDSA_Sign feature CRYS_ECDSA_SignUserContext_t * pSignUserContext. The documentation of this type says that "The context saves the state of the operation and must be saved by the user till the end of the APIs flow."

Yet the signing function is atomic, and thus it is unclear what the "API flow" means in this case. Can the user context be discarded after a successful signing operation? What is its correct use?

Thanks,

Damian

[Einar Thorsrud]

Hi,

You can safely discard the context after a successful signing operation. The statement about the context is a generic statement that is repeated in the API documentation for most context types. It does not make sense in the CRYS_ECDSA_Sign() case as that is atomic, but it makes sense in many other operations where you have a init/update/finish pattern.

[DamianV]

Thanks for the answer Einar!

What is the purpose of the context for an atomic function like this one? Does it act as a buffer? Or is it safe to pass a NULL pointer to save resources?

[Einar Thorsrud]

You still need the context. It is used to provide a memory buffer used during the calculations.