OpenSSL::PKey::EC::Group#seed=

static VALUE ossl_ec_group_set_seed(VALUE self, VALUE seed)
{
    EC_GROUP *group = NULL;

    GetECGroup(self, group);
    StringValue(seed);

    if (EC_GROUP_set_seed(group, (unsigned char *)RSTRING_PTR(seed), RSTRING_LEN(seed)) != (size_t)RSTRING_LEN(seed))
        ossl_raise(eEC_GROUP, "EC_GROUP_set_seed");

    return seed;
}