EC_GROUP_get_cofactor
int EC_GROUP_get_cofactor(const EC_GROUP *group, BIGNUM *cofactor, BN_CTX *ctx);
LCRYPTO_ALIAS(EC_GROUP_get_cofactor);
if (!EC_GROUP_get_cofactor(group, cofactor, NULL)) {
LCRYPTO_USED(EC_GROUP_get_cofactor);
if (!EC_GROUP_get_cofactor(group, cofactor, ctx))
if (!EC_GROUP_get_cofactor(group, guessed_cofactor, ctx)) {
if (EC_GROUP_get_cofactor(group, cofactor, NULL) != 1)