Each comes in its own sourcefile called `example_<operation>.c`. To see which functions to call to perform each operations, please read the code.
The application measures the processing times of the example operations. The table below shows the expected runtime values
for software and hardware backends as well as secure elements, measured on the nRF52840dk (this is only to show the expected difference, values will differ on other platforms).
> Currently this implementation only supports Microchip ATECCX08A devices. Those devices need to be configured and locked to be able to correctly use them.
> This implementation assumes that you have done that and that you know your device's configuration.
You can build this app either with one secure element or two secure elements (`SECURE_ELEMENT=1` or `SECURE_ELEMENT=2`). To be able to use your device, make sure, you've completed the following procedure.
In the application folder you can find a file called `custom_atca_params.h`, which overwrites the device parameters in `atca_params.h` in the cryptoauthlib package folder.
To use more than one secure element, you need to specify device parameters for both of them.
This application assumes that you connect two devices with different I2C addresses on the same I2C bus.
Alternatively you can connect two devices with the same address on separate buses.
You can modify `custom_atca_params.h` according to your device configurations and requirements.
For PSA Crypto, you also need to define a location value. Here these are defined as `PSA_ATCA_LOCATION_DEV0` and `PSA_ATCA_LOCATION_DEV1`. They can be any value between `PSA_KEY_LOCATION_SE_MIN` and `PSA_KEY_LOCATION_SE_MAX`.
A special value is `PSA_KEY_LOCATION_PRIMARY_SECURE_ELEMENT`, which can be used when only one secure element is needed.
Below the `ATCA_PARAMS` definitions, you can see the slot configurations.
Here you need to specify for each connected secure element what kind of key can be stored in which slot, and whether a slot is already occupied. The structure is declared in `pkg/cryptoauthlib/include/atca.h` and contains the following elements:
1.`key_type_allowed` (takes `psa_key_type_t`)
2.`key_persistent` (is 0, can be ignored for now, since PSA does not yet support persistent storage)
3.`slot_occupied` (should be 0 at start up, PSA will use this to mark slots as occupied)
The list in `custom_atca_params.h` contains an example configuration. If your device configuration is not compatible, you'll need to change the values as necessary.
This is required, so the implementation can allocate free key slots and can generate and import new keys. If the device configuration does not match the values in the list or if your key slots are not writeable, you will get execution errors.
The current implementation does not support the use of keys that are already stored on the device.
## Note
If you need more information about the build options, please refer to the API documentation.
