The short name of the ObjectId, as defined in <openssl/objects.h>.
static VALUE
ossl_asn1obj_get_sn(VALUE self)
{
VALUE val, ret = Qnil;
int nid;
val = ossl_asn1_get_value(self);
if ((nid = OBJ_txt2nid(StringValueCStr(val))) != NID_undef)
ret = rb_str_new2(OBJ_nid2sn(nid));
return ret;
}