Abstract: A tamper-resistant fastener includes a non-circular drive recess optionally with a non-circular center post. Preferably the recess and center post are at least partially ellipsoidal cylinders that are concentric and aligned (i.e. they share a common major axis direction). This configuration forms a slot having preferably a substantially uniform width into which an authorized driver is inserted. The length of the major maximum dimension of the post is selected so that a circular arc tangent to the maximum radius of the post will pass closely to or intersect the minimum radial dimension of the recess.