private static GroupElementP1 P2ToP1(ref GroupElementP2 p)
{
var r = new GroupElementP1();
/* XX=X1^2 */
r.X = FieldElementOperations.Squared(ref p.X);
/* YY=Y1^2 */
r.Z = FieldElementOperations.Squared(ref p.Y);
/* B=2*Z1^2 */
r.T = FieldElementOperations.DoubleSquare(ref p.Z);
/* A=X1+Y1 */
r.Y = FieldElementOperations.Add(ref p.X, ref p.Y);
/* AA=A^2 */
var t0 = FieldElementOperations.Squared(ref r.Y);
/* Y3=YY+XX */
r.Y = FieldElementOperations.Add(ref r.Z, ref r.X);
/* Z3=YY-XX */
r.Z = FieldElementOperations.Sub(ref r.Z, ref r.X);
/* X3=AA-Y3 */
r.X = FieldElementOperations.Sub(ref t0, ref r.Y);
/* T3=B-Z3 */
r.T = FieldElementOperations.Sub(ref r.T, ref r.Z);
return(r);
}
