Why does the ECC module require the softdevice to be initialised?

RE: Why does the ECC module require the softdevice to be initialised?

bjorn-spockeli — Thu, 02 Feb 2017 09:45:26 GMT

So ecc_p256_keypair_gen() returns NRF_SUCCESS if you call it after SOFTDEVICE_HANDLER_INIT(), before calling softdevice_enable(), which in turn calls sd_ble_enable?

I looked through the code in uECC.c and calling ecc_p256_keypair_gen will result in the following call stack.

ecc_p256_keypair_gen --> uECC_make_key -->uECC_generate_random_int-->g_rng_function

The g_rng_function is set to nrf_drv_rng_block_rand in ecc_init() in ecc.c

I assume that you have called ecc_init before calling ecc_p256_keypair_gen, but If g_rng_function in uECC_generate_random_int does not return then you will get NRF_ERROR_INTERNAL since the return value 0 is propagated up to ecc_p256_keypair_gen. It could be that you need to request the LFCLK and/or HFCLK before calling ecc_p256_keypair_gen if you have not called SOFTDEVICE_HANDLER_INIT() which configures the clock source for the SD.

RE: Why does the ECC module require the softdevice to be initialised?

jm_laird — Wed, 01 Feb 2017 19:18:17 GMT

nRF52 softdevice 3.0.0 using SDK v12.0.0, calling ecc_p256_keypair_gen() causes the NRF_ERROR_INTERNAL response. If it's placed after the softdevice handler initiation functions then NRF_SUCCESS is returned.

RE: Why does the ECC module require the softdevice to be initialised?

bjorn-spockeli — Mon, 30 Jan 2017 12:01:48 GMT

Hi Jm_Laird, Which SDK and SoftDevice version are you using? Which call returned the internal error code?

As far as I know there is no dependency between the micro-ecc library and the SoftDevice. The nrf_crypto library, which wraps the micro-ecc library in the SDK, is an independent module that implements SV-calls to the micro_ecc_lib_nrf52.lib that is compiled from the micro-ecc source.