http://i2p-javadocs.i2p/net/i2p/crypto/eddsa/math/class-use/Curve.html
GroupElement ( Curve curve, GroupElement.Representation repr, FieldElement X, FieldElement Y, FieldElement Z, FieldElement T) Creates a group element for a curve, without any pre-computation. GroupElement ( Curve curve, GroupElement.Representation repr, FieldElement X, FieldElement Y, FieldElement Z, FieldElement T,
boolean precomputeDouble) Creates a group element for a curve, with optional pre-computation.