I am using ES256 to create a JWT using mbedTLS. I just had a few questions as I am new to cryptography and mbedTLS.
For the x and y values determining the points of a curve, do those correspond to mbedtls_ecp_keypair.d and mbedtls_ecp_keypair.Q or mbedtls_ecp_point.private_X and mbedtls_ecp_point.private_Y ?
I am using mbedtls_write_binary on the r and s values obtained from mbedtls_ecdsa_sign. These are returning arrays of mostly 0s followed by 64 or 66 characters. Are these last 64 or 66 characters the hexadecimal octets I should be concatenating to form the JWT signature?