public static EllipticCurvePoint addPoints(EllipticCurve curve, EllipticCurvePoint point1, EllipticCurvePoint point2)
{
BigInteger xResult = calculateX(curve, point1, point2);
return(new EllipticCurvePoint {
x = xResult, y = calculateY(curve, point1, point2, xResult)
});
}
public static EllipticCurvePoint doublePoint(EllipticCurve curve, EllipticCurvePoint point)
{
BigInteger xResult = calculateX(curve, point);
return(new EllipticCurvePoint {
x = xResult, y = calculateY(curve, point, xResult)
});
}
private static EllipticCurvePoint getResult(int[] bits, int index, EllipticCurve curve, EllipticCurvePoint auxPoint)
{
EllipticCurvePoint result = auxPoint;
while (index < bits.Length)
{
auxPoint = PointDoubling.doublePoint(curve, auxPoint);
if (bits[index] == 1)
{
result = PointAddition.addPoints(curve, result, auxPoint);
}
index++;
}
return(result);
}
public static EllipticCurvePoint multiplyPoint(BigInteger prk, EllipticCurvePoint point, EllipticCurve curve)
{
if (prk == 0)
{
return new EllipticCurvePoint {
x = 0, y = 0
}
}
;
int[] bits = BitOperations.getBits(prk);
int index = 0;
EllipticCurvePoint initial = point;
while (bits[index] == 0)
{
initial = PointDoubling.doublePoint(curve, initial);
index++;
}
return(getResult(bits, index + 1, curve, initial));
}
private static BigInteger calculateYDenominator(EllipticCurve curve, EllipticCurvePoint point1, EllipticCurvePoint point2)
{
BigInteger yDenominator = point2.x - point1.x;
return(ModulusLogic.inverseModuloN(ModulusLogic.convertToModulus(yDenominator, curve.n), curve.n));
}
private static BigInteger calculateYNumerator(EllipticCurve curve, EllipticCurvePoint point1, EllipticCurvePoint point2, BigInteger xResult)
{
BigInteger yNumerator = (point2.y - point1.y) * (point1.x - xResult) - point1.y * (point2.x - point1.x);
return(ModulusLogic.convertToModulus(yNumerator, curve.n));
}
/*---------------------------------------------------------------------------------------------------------------------------
* Y
* ---------------------------------------------------------------------------------------------------------------------------*/
private static BigInteger calculateY(EllipticCurve curve, EllipticCurvePoint point1, EllipticCurvePoint point2, BigInteger xResult)
{
return(ModulusLogic.convertToModulus(calculateYNumerator(curve, point1, point2, xResult) * calculateYDenominator(curve, point1, point2), curve.n));
}
private static BigInteger calculateXNumerator(EllipticCurve curve, EllipticCurvePoint point1, EllipticCurvePoint point2)
{
BigInteger xNumerator = (point2.y - point1.y) * (point2.y - point1.y) - (point1.x + point2.x) * (point2.x - point1.x) * (point2.x - point1.x);
return(ModulusLogic.convertToModulus(xNumerator, curve.n));
}
private static BigInteger calculateYNumerator(EllipticCurve curve, EllipticCurvePoint point, BigInteger xResult)
{
BigInteger yNumerator = (3 * point.x * point.x + curve.a) * (point.x - xResult) - 2 * point.y * point.y;
return(ModulusLogic.convertToModulus(yNumerator, curve.n));
}
private static BigInteger calculateXDenominator(EllipticCurve curve, EllipticCurvePoint point)
{
BigInteger xDenominator = 4 * point.y * point.y;
return(ModulusLogic.inverseModuloN(ModulusLogic.convertToModulus(xDenominator, curve.n), curve.n));
}
private static BigInteger calculateXNumerator(EllipticCurve curve, EllipticCurvePoint point)
{
BigInteger xNumerator = 9 * point.x * point.x * point.x * point.x + 6 * curve.a * point.x * point.x + curve.a * curve.a - 8 * point.x * point.y * point.y;
return(ModulusLogic.convertToModulus(xNumerator, curve.n));
}
/*---------------------------------------------------------------------------------------------------------------------------
* X
* ---------------------------------------------------------------------------------------------------------------------------*/
private static BigInteger calculateX(EllipticCurve curve, EllipticCurvePoint point)
{
return(ModulusLogic.convertToModulus((calculateXNumerator(curve, point) * calculateXDenominator(curve, point)), curve.n));
}
