twice method

ECPointFp twice()

Implementation

ECPointFp twice() {
  if (isInfinity()) return this;
  if (y!.toBigInteger().sign == 0) return curve.infinity;

  final x1 = x!.toBigInteger();
  final y1 = y!.toBigInteger();
  final z1 = z;
  final q = curve.q;
  final a = curve.a.toBigInteger();

  final w1 = (x1 * x1 * BigInt.from(3) + a * (z1 * z1)) % q;
  final w2 = (y1 * BigInt.from(2) * z1) % q;
  final w3 = (y1 * y1) % q;
  final w4 = (w3 * x1 * z1) % q;
  final w5 = (w2 * w2) % q;
  final w6 = (w1 * w1 - w4 * BigInt.from(8)) % q;

  final x3 = (w2 * w6) % q;
  final y3 = (w1 * (w4 * BigInt.from(4) - w6) - w5 * BigInt.from(2) * w3) % q;
  final z3 = (w2 * w5) % q;

  return ECPointFp(curve, curve.fromBigInteger(x3), curve.fromBigInteger(y3), z3);
}