Slowness in verification of a ecdsa secp256r1 signature using S32K Microcontroller (clock speed 112MHz) - bare metal implementation - mbed-tls

3 Sep 2022


      I am verifying a signature generated using ecdsa secp256r1. The signature is getting verified but the time taken by the verification step is too long. It takes 4-5 seconds to verify the signature. The implementation is bare metal i.e. no RTOS (one realizes the use of RTOS but still the time is too long). Can you please guide a way around for this issue. How to make it work faster , the ideal verification time would be 30ms - 60ms. 
Here is a gist of my code
mbedtls_ecp_curve_info *curve_info = NULL;
mbedtls_ecdsa_context ecdsa_context;
/// Initialization
mbedtls_ecdsa_init(&ecdsa_context);
curve_info = mbedtls_ecp_curve_info_from_tls_id(23);  /// 23 is tls_id of secp256r1
mbedtls_ecp_group_load(&ecdsa_context.grp, curve_info->grp_id);
/// Processing
result = mbedtls_ecp_point_read_binary(
    	    &ecdsa_context.grp,
    	    &ecdsa_context.Q,
    	    public_key_data, // public key data in uncompressed format i.e. including leading 0x04
    	    sizeof(public_key_data)
    	);
                                                                                                                                  /// 32                            /// 71 
status_verify_signature = mbedtls_ecdsa_read_signature(&ecdsa_context, hash, sizeof(hash), signature, sizeof(sig)); /// converts the signature data to ASN1, verifies the signature
Thank you :)