Arm Mbed OS support forum

Hard-coding pre-computed points for ecp_mul_comb() on ECDSA signature verification (ecp.h)

If I am using MBEDTLS_ECP_DP_SECP256R1 curve, then is it possible to used fixed (pre-calculated) value for the “mbedtls_ecp_point T; /!< pre-computed points for ecp_mul_comb() */”.
The calculaton process using long time on micro controller(msp430f6779) with low processing speed. So I like to hard-code the value on signature verification process. Does it work for all cases ?

typedef struct
{
mbedtls_ecp_group_id id; /*!< internal group identifier /
mbedtls_mpi P; /
!< prime modulus of the base field /
mbedtls_mpi A; /
!< 1. A in the equation, or 2. (A + 2) / 4 /
mbedtls_mpi B; /
!< 1. B in the equation, or 2. unused /
mbedtls_ecp_point G; /
!< generator of the (sub)group used /
mbedtls_mpi N; /
!< 1. the order of G, or 2. unused /
size_t pbits; /
!< number of bits in P /
size_t nbits; /
!< number of bits in 1. P, or 2. private keys /
unsigned int h; /
!< internal: 1 if the constants are static */
int (*modp)(mbedtls_mpi ); /!< function for fast reduction mod P */
int (*t_pre)(mbedtls_ecp_point *, void ); /!< unused */
int (*t_post)(mbedtls_ecp_point *, void ); /!< unused */
void t_data; /!< unused */
mbedtls_ecp_point T; /!< pre-computed points for ecp_mul_comb() /
size_t T_size; /
!< number for pre-computed points */
}
mbedtls_ecp_group;

Hi @Kamaldevkr
Thank you for your question!
Unfortunately, Mbed TLS does not support hard-coding pre-computed points. This is in our plans, however it keeps getting lower in the priority list (which is long as you can imagine)
Have you considered using the non-blocking ECC feature?
Regards,
Mbed TLS Support
Ron