crypto/src/math/ec/multiplier/NafR2LMultiplier.cs


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namespace Org.BouncyCastle.Math.EC.Multiplier
{
    /**
     * Class implementing the NAF (Non-Adjacent Form) multiplication algorithm (right-to-left).
     */
    public class NafR2LMultiplier 
        : AbstractECMultiplier
    {
        protected override ECPoint MultiplyPositive(ECPoint p, BigInteger k)
        {
            int[] naf = WNafUtilities.GenerateCompactNaf(k);

            ECPoint R0 = p.Curve.Infinity, R1 = p;

            int zeroes = 0;
            for (int i = 0; i < naf.Length; ++i)
            {
                int ni = naf[i];
                int digit = ni >> 16;
                zeroes += ni & 0xFFFF;

                R1 = R1.TimesPow2(zeroes);
                R0 = R0.Add(digit < 0 ? R1.Negate() : R1);

                zeroes = 1;
            }

            return R0;
        }
    }
}