Is there a quick math trick to determine if two points share the same higher level endomorphic ring? Just by their X and Y?
By higher-level, I mean 149 or 631. 2 and 3 are obvious. I know that all of the points that share the same subgroup sum up to O. It's also possible to build up the subgroup entirely, but is this really required, in order to make such a check, that the other point is in the same subgroup?