openssl3 ecc

openssl3_ecc.c

#include <openssl/ec.h>
#include <openssl/obj_mac.h>
#include <openssl/objects.h>
#include <openssl/evp.h>
#include <openssl/pem.h>
#include <openssl/core_names.h>

void print_hex(const unsigned char *buf, size_t buf_len)
{
    for (size_t i = 0; i < buf_len; i++)
    {
        printf("%02x", buf[i]);
    }
    printf("\n");
}

int main()
{
    EVP_PKEY *pkey = EVP_PKEY_new();
    EVP_PKEY_CTX *pctx = EVP_PKEY_CTX_new_id(EVP_PKEY_EC, NULL);
    EVP_PKEY_keygen_init(pctx);
    EVP_PKEY_CTX_set_ec_paramgen_curve_nid(pctx, NID_X9_62_prime256v1);
    EVP_PKEY_keygen(pctx, &pkey);

    if (EVP_PKEY_set_utf8_string_param(pkey, OSSL_PKEY_PARAM_EC_POINT_CONVERSION_FORMAT, "compressed") != 1)
    {
        printf("EVP_PKEY_set_utf8_string_param failed\n");
        return 1;
    }

    OSSL_PARAM *params;
    if (EVP_PKEY_todata(pkey, EVP_PKEY_PUBLIC_KEY, &params) == 0)
    {
        printf("EVP_PKEY_todata failed\n");
        return 1;
    }

    OSSL_PARAM *params_pub = OSSL_PARAM_locate(params, OSSL_PKEY_PARAM_PUB_KEY);
    if (params_pub == NULL)
    {
        printf("OSSL_PARAM_locate failed\n");
        return 1;
    }

    printf("params: %s\n", params_pub->key);
    print_hex((unsigned char *)params_pub->data, params_pub->data_size);

    OSSL_PARAM_free(params);
    EVP_PKEY_free(pkey);
    EVP_PKEY_CTX_free(pctx);

    return 0;
}