147 lines
3.8 KiB
C#
147 lines
3.8 KiB
C#
using System;
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using BigInt;
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using System.Text;
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using sharp.extensions;
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namespace Crypto.EC
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{
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public class EllipticCurve
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{
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public UInteger a { get; private set; }
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public UInteger b { get; private set; }
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public UInteger n { get; private set; }
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public int h { get; private set; }
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public CurvePoint G { get; private set; }
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public IntField Fp { get; private set; }
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public EllipticCurve(UInteger p,UInteger a,UInteger b,UInteger xG,UInteger yG,UInteger n,int h)
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{
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this.Fp = new IntField(p);
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this.a = a;
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this.b = b;
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this.n = n;
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this.h = h;
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this.G = new CurvePoint(this, xG, yG);
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if (!isOnCurve(this.G)){
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throw new ArgumentException("G is not part of the curve");
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}
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}
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public UInteger Y2(UInteger x){
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UInteger yy = x;
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Console.WriteLine("Y(x): X = {0}",x.toHexString());
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Console.WriteLine("Y(x): x^2 = {0}",yy.Pow(2).toHexString());
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yy = yy.Pow(3);
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Console.WriteLine("Y(x): x^3 = {0}",yy.toHexString());
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yy += (a * x);
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Console.WriteLine("Y(x): x^3 + ax = {0}",yy.toHexString());
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yy += b;
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Console.WriteLine("Y(x) x^3 + ax + b = {0}",yy.toHexString());
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yy %= this.Fp.FieldModulo;
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Console.WriteLine("Y(x) mod p = {0}",yy.toHexString());
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return yy;
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}
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public bool isOnCurve(CurvePoint p){
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UInteger py2 = p.Y.Pow(2);
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UInteger pcy2 = Y2(p.X);
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Console.WriteLine("CHECK A: {0}",py2.toHexString());
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Console.WriteLine("CHECK B: {0}",pcy2.toHexString());
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return (py2 == pcy2);
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}
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public CurvePoint Add(CurvePoint p1, CurvePoint p2)
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{
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if (((object)p1 == null) || ((object)p2 == null))
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{
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throw new ArgumentException("CurvePoints to be added must not be null");
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}
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if (p1.Curve != p2.Curve)
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{
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throw new ArgumentException("Curvepoints to be added must belong to the same curve!");
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}
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if (p1 == p2)
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{
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UInteger s = p1.X.Pow(2);
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s *= 3;
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s += p1.Curve.a;
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s /= (p1.Y << 1);
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//(((p1.X.Pow(2) * 3) + p1.Curve.a) / (p1.Y << 1));
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UInteger xR = (s.Pow(2) - (p1.X << 1));
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UInteger yR = ((s * (p1.X - xR)) - p1.Y);
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return new CurvePoint(p1.Curve, xR, yR);
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}
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if (p1.X == p2.X)
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{
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throw new NotImplementedException("Eternity point not implemented");
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}
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else
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{
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UInteger s = (((p1.Y - p2.Y) / (p1.X - p2.X)));
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UInteger xR = (s.Pow(2) - p1.X - p2.X);
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UInteger yR = ((s * (p1.X - xR)) - p1.Y);
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return new CurvePoint(p1.Curve, xR, yR);
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}
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throw new NotImplementedException("Point addition not yet implemented");
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}
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/* public CurvePoint getPoint(T x){
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x = new T(x, this.Fp);
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return new CurvePoint(this,x,Y(x));
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}
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*/
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public override string ToString()
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{
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StringBuilder sb = new StringBuilder();
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sb.AppendFormat("[EllipticCurve] Fp={0}\n",(Fp == null) ? "" : Fp.ToString());
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sb.AppendFormat("[EllipticCurve] a={0}\n",a.toHexString());
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sb.AppendFormat("[EllipticCurve] b={0}\n",b.toHexString());
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sb.AppendFormat("[EllipticCurve] Gx={0}\n",G.X.toHexString());
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sb.AppendFormat("[EllipticCurve] Gy={0}\n",G.Y.toHexString());
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sb.AppendFormat("[EllipticCurve] G on curve? {0}",isOnCurve(G));
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return sb.ToString();
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}
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public static EllipticCurve createSecp256k1(){
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UInteger p = (UInteger.ONE << 256);
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p -= UInteger.ONE;
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p -= (UInteger.ONE << 32);
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p -= (UInteger.ONE << 9);
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p -= (UInteger.ONE << 8);
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p -= (UInteger.ONE << 7);
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p -= (UInteger.ONE << 6);
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p -= (UInteger.ONE << 4);
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UInteger xG = UInteger.fromHexString("79BE667EF9DCBBAC55A06295CE870B07029BFCDB2DCE28D959F2815B16F81798");
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UInteger yG = UInteger.fromHexString("483ADA7726A3C4655DA4FBFC0E1108A8FD17B448A68554199C47D08FFB10D4B8");
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UInteger n = UInteger.fromHexString("FFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFEBAAEDCE6AF48A03BBFD25E8CD0364141");
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return new EllipticCurve(p, new UInteger(0), new UInteger(7), xG, yG, n, 1);
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}
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}
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}
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