RE: verifying signature ecc dsa with secp256r1 zephyr

Vidar Berg — Mon, 02 Aug 2021 13:30:00 GMT

Hello,

I suspect it might be related to the byte endianess of your inputs. uECC in the nRF5 SDK is compiled for little-endian which is converted to big endian at the nRF crypto layer above (see nrf_crypto_ecc_byte_order_invert). There's is also a remark in the tinycrypt documentation about endianness which may be relevant:

"Integer representation: To reduce code size, all large integers are represented using little-endian words - so the least significant word is first. You can use the 'ecc_bytes2native()' and 'ecc_native2bytes()' functions to convert between the native integer representation and the standardized octet representation." https://github.com/intel/tinycrypt/blob/master/documentation/tinycrypt.rst

Another alternative you may consider is to use the Nordic security module as discussed in this thread: https://devzone.nordicsemi.com/f/nordic-q-a/68985/trying-to-implement-ecdh-key-exchange-using-tinycrypt-but-the-random-num-gen-keeps-crashing/284564#284564