protected override ECPoint MultiplyPositive(ECPoint p, BigInteger k)
{
int num = Math.Max(2, Math.Min(16, GetWindowSize(k.BitLength)));
WNafPreCompInfo wNafPreCompInfo = WNafUtilities.Precompute(p, num, includeNegated: true);
ECPoint[] preComp = wNafPreCompInfo.PreComp;
ECPoint[] preCompNeg = wNafPreCompInfo.PreCompNeg;
int[] array = WNafUtilities.GenerateCompactWindowNaf(num, k);
ECPoint eCPoint = p.Curve.Infinity;
int num2 = array.Length;
if (num2 > 1)
{
int num3 = array[--num2];
int num4 = num3 >> 16;
int num5 = num3 & 0xFFFF;
int num6 = Math.Abs(num4);
ECPoint[] array2 = (num4 < 0) ? preCompNeg : preComp;
if (num6 << 2 < 1 << num)
{
int num7 = LongArray.BitLengths[num6];
int num8 = num - num7;
int num9 = num6 ^ (1 << num7 - 1);
int num10 = (1 << num - 1) - 1;
int num11 = (num9 << num8) + 1;
eCPoint = array2[num10 >> 1].Add(array2[num11 >> 1]);
num5 -= num8;
}
else
{
eCPoint = array2[num6 >> 1];
}
eCPoint = eCPoint.TimesPow2(num5);
}
while (num2 > 0)
{
int num12 = array[--num2];
int num13 = num12 >> 16;
int e = num12 & 0xFFFF;
int num14 = Math.Abs(num13);
ECPoint[] array3 = (num13 < 0) ? preCompNeg : preComp;
ECPoint b = array3[num14 >> 1];
eCPoint = eCPoint.TwicePlus(b);
eCPoint = eCPoint.TimesPow2(e);
}
return(eCPoint);
}
/**
* Multiplies <code>this</code> by an integer <code>k</code> using the
* Window NAF method.
* @param k The integer by which <code>this</code> is multiplied.
* @return A new <code>ECPoint</code> which equals <code>this</code>
* multiplied by <code>k</code>.
*/
protected override ECPoint MultiplyPositive(ECPoint p, BigInteger k)
{
// Clamp the window width in the range [2, 16]
int width = System.Math.Max(2, System.Math.Min(16, GetWindowSize(k.BitLength)));
WNafPreCompInfo wnafPreCompInfo = WNafUtilities.Precompute(p, width, true);
ECPoint[] preComp = wnafPreCompInfo.PreComp;
ECPoint[] preCompNeg = wnafPreCompInfo.PreCompNeg;
int[] wnaf = WNafUtilities.GenerateCompactWindowNaf(width, k);
ECPoint R = p.Curve.Infinity;
int i = wnaf.Length;
/*
* NOTE: We try to optimize the first window using the precomputed points to substitute an
* addition for 2 or more doublings.
*/
if (i > 1)
{
int wi = wnaf[--i];
int digit = wi >> 16, zeroes = wi & 0xFFFF;
int n = System.Math.Abs(digit);
ECPoint[] table = digit < 0 ? preCompNeg : preComp;
// Optimization can only be used for values in the lower half of the table
if ((n << 2) < (1 << width))
{
int highest = LongArray.BitLengths[n];
// TODO Get addition/doubling cost ratio from curve and compare to 'scale' to see if worth substituting?
int scale = width - highest;
int lowBits = n ^ (1 << (highest - 1));
int i1 = ((1 << (width - 1)) - 1);
int i2 = (lowBits << scale) + 1;
R = table[i1 >> 1].Add(table[i2 >> 1]);
zeroes -= scale;
}
else
{
R = table[n >> 1];
}
R = R.TimesPow2(zeroes);
}
while (i > 0)
{
int wi = wnaf[--i];
int digit = wi >> 16, zeroes = wi & 0xFFFF;
int n = System.Math.Abs(digit);
ECPoint[] table = digit < 0 ? preCompNeg : preComp;
ECPoint r = table[n >> 1];
R = R.TwicePlus(r);
R = R.TimesPow2(zeroes);
}
return(R);
}
