sharp-crypto/EC/CurvePoint.cs

using System;
using BigInt;
using System.Text;
using System.Runtime.CompilerServices;

namespace Crypto.EC
{
	public class CurvePoint
	{
		public static readonly CurvePoint INFINITY = new CurvePoint();

		public CurvePoint(EllipticCurve curve,Integer x,Integer y){
			Curve = curve;
			X = x;
			Y = y;
		}

		private CurvePoint(){
			this.Curve = null;
			this.X = 0;
			this.Y = 0;
		}

		public string toHexString()
		{
			StringBuilder sb = new StringBuilder();
			sb.Append(((UInteger)X).toHexString());
			sb.Append(".");
			sb.Append(((UInteger)Y).toHexString());
			return sb.ToString();
		}

		public override string ToString()
		{
			if ((object)this == (object)INFINITY){
				return String.Format("[CurvePoint INFINITY]");
			}
			return String.Format("[CurvePoint X={0} Y={1}]",X.ToString(),Y.ToString());
		}

		public EllipticCurve Curve { get; private set; }
		public Integer X { get; private set; }
		public Integer Y { get; private set; }

		public bool isOnCurve(){
			return this.Curve.isOnCurve(this);
		}

		public bool isInfinity(){
			return ((object)this == (object)INFINITY);
		}

		public CurvePoint Negated(){
			return new CurvePoint(Curve, X, Curve.Fp.AdditiveInverse(Y));
		}

		public static CurvePoint operator +(CurvePoint p1, CurvePoint p2)
		{
			if ((object)p1 == (object)INFINITY){
				return p2;
			}
			if ((object)p2 == (object)INFINITY){
				return p1;
			}

			return p1.Curve.Add(p1, p2);
		}

		public static CurvePoint operator -(CurvePoint p1, CurvePoint p2)
		{
			if ((object)p1 == (object)INFINITY){
				return p2;
			}
			if ((object)p2 == (object)INFINITY){
				return p1;
			}
			return p1.Curve.Add(p1, p2.Negated());
		}

		public static CurvePoint operator *(CurvePoint p1, Integer n)
		{
			if ((object)p1 == (object)INFINITY){
				return INFINITY;
			}

			if (p1.Y == Integer.ZERO){
				return INFINITY;
			}

			if (n.isZero()){
				throw new NotImplementedException("CurevPoint * 0");
			}

			CurvePoint result = null;
			CurvePoint p = p1;

			int i;
			int bitwidth = n.Log2();

			if (bitwidth < 0){
				bitwidth = -bitwidth;
			}

			for (i = 0; i < bitwidth; i++)
			{
				if (n[i])
					break;
				
				p += p;
			}

			result = p;

			for (i++; i <= bitwidth; i++)
			{
				p += p;
				if (n[i]){
					result = p + result;
				}
			}

			return result;
		}

		public static bool operator ==(CurvePoint p1, CurvePoint p2)
		{
			if (((object)p1 == null)||((object)p2==null)){
				return false;
			}
			return (p1.X == p2.X) && (p1.Y == p2.Y);
		}
		public static bool operator !=(CurvePoint p1, CurvePoint p2)
		{
			return (p1.X != p2.X) || (p1.Y != p2.Y);
		}

		public override bool Equals(object obj)
		{
			if (this.GetType().IsInstanceOfType(obj)){
				return (this == (CurvePoint)obj);
			} else {
				return false;
			}
		}


	}
}