doublePoint method

@override EDPoint doublePoint()

Double an Edwards curve point.

This method computes the result of doubling an Edwards curve point on the same curve. It calculates the new coordinates and returns them as a list.

Parameters:

• x1: x-coordinate of the point.
• y1: y-coordinate of the point.
• z1: z-coordinate of the point.
• t1: t-coordinate of the point.
• p: The prime modulus of the curve.
• a: The 'a' parameter of the curve equation.

Returns:

• A list of BigInt values representing the new coordinates x3, y3, z3, t3 after doubling the point.

Implementation

@override
EDPoint doublePoint() {
  final BigInt x1 = _coords[0];
  final BigInt t1 = _coords[3];
  final BigInt p = curve.p;
  final BigInt a = curve.a;

  if (x1 == BigInt.zero || t1 == BigInt.zero) {
    return EDPoint.infinity(curve: curve);
  }

  final newCoords = _double(x1, _coords[1], _coords[2], t1, p, a);
  if (newCoords[0] == BigInt.zero || newCoords[3] == BigInt.zero) {
    return EDPoint.infinity(curve: curve);
  }

  return EDPoint._(curve, newCoords, order: order);
}