PrimeFieldCurve.cs

using System;
using System.Collections.Generic;
using System.Numerics;
using System.Security.Cryptography;
using System.Text;
using System.Xml;
 
namespace Waher.Security.EllipticCurves
{
    public abstract class PrimeFieldCurve : EllipticCurve
    {
        protected readonly ModulusP modP;
 
        protected readonly ModulusP modN;
 
        protected readonly BigInteger p;
 
        public PrimeFieldCurve(BigInteger Prime, PointOnCurve BasePoint, BigInteger Order,
            int Cofactor)
            : this(Prime, BasePoint, Order, Cofactor, null)
        {
        }
 
        public PrimeFieldCurve(BigInteger Prime, PointOnCurve BasePoint, BigInteger Order,
            int Cofactor, byte[] Secret)
            : base(BasePoint, Order, Cofactor, Secret)
        {
            if (Prime <= BigInteger.One)
                throw new ArgumentException("Invalid prime base.", nameof(Prime));
 
            this.p = Prime;
            this.modP = new ModulusP(Prime);
            this.modN = new ModulusP(Order);
        }
 
        public BigInteger Prime => this.p;
 
        public override PointOnCurve ScalarMultiplication(byte[] N, PointOnCurve P, bool Normalize)
        {
            PointOnCurve Result = base.ScalarMultiplication(N, P, Normalize);
 
            if (Normalize)
                Result.Normalize(this);
 
            return Result;
        }
 
        public override byte[] GenerateSecret()
        {
            byte[] B = new byte[this.orderBytes];
            BigInteger D;
 
            do
            {
                lock (rnd)
                {
                    rnd.GetBytes(B);
                }
 
                B[this.orderBytes - 1] &= this.msbOrderMask;
 
                D = ToInt(B);
            }
            while (D.IsZero || D >= this.n);
 
            return B;
        }
 
        public ModulusP ModulusP => this.modP;
 
        public ModulusP ModulusN => this.modN;
 
    }
}