Edwards25519.cs

using System;
using System.Globalization;
using System.IO;
using System.Numerics;
 
namespace Waher.Security.EllipticCurves
{
    public class Edwards25519 : EdwardsTwistedCurve
    {
        private static readonly BigInteger p0 = BigInteger.Pow(2, 255) - 19;
        private static readonly BigInteger d0 = BigInteger.Parse("37095705934669439343138083508754565189542113879843219016388785533085940283555");
        private static readonly BigInteger n0 = BigInteger.Pow(2, 252) + BigInteger.Parse("14def9dea2f79cd65812631a5cf5d3ed", NumberStyles.HexNumber);
        private static readonly BigInteger BasePointX = BigInteger.Parse("15112221349535400772501151409588531511454012693041857206046113283949847762202");
        private static readonly BigInteger BasePointY = BigInteger.Parse("46316835694926478169428394003475163141307993866256225615783033603165251855960");
        private readonly bool hashSecret;
 
        public Edwards25519()
            : this(null, true)
        {
        }
 
        public Edwards25519(byte[] Secret)
            : this(Secret, true)
        {
        }
 
        public Edwards25519(byte[] Secret, bool HashSecret)
            : base(p0, new PointOnCurve(BasePointX, BasePointY), d0, n0, 8, Secret)
        {
            this.hashSecret = HashSecret;
        }
 
        public override string CurveName => "Edwards25519";
 
        public override int CoordinateBits => 254;
 
        public override Tuple<byte[], byte[]> CalculatePrivateKey(byte[] Secret)
        {
            byte[] Bin = Hashes.ComputeSHA512Hash(Secret);
            byte[] AdditionalInfo = new byte[32];
            byte[] PrivateKey = new byte[32];
 
            if (this.hashSecret)
                Buffer.BlockCopy(Bin, 0, PrivateKey, 0, 32);
            else
                Buffer.BlockCopy(Secret, 0, PrivateKey, 0, Math.Min(32, Secret.Length));
 
            Buffer.BlockCopy(Bin, 32, AdditionalInfo, 0, 32);
 
            PrivateKey[0] &= 0xf8;
            PrivateKey[31] &= 0x3f;
            PrivateKey[31] |= 0x40;
 
            return new Tuple<byte[], byte[]>(PrivateKey, AdditionalInfo);
        }
 
        public override byte[] Sign(byte[] Data, bool BigEndian)
        {
            return EdDSA.Sign(Data, BigEndian, this.PrivateKey, this.AdditionalInfo, Hashes.ComputeSHA512Hash, this);
        }
 
        public override byte[] Sign(Stream Data, bool BigEndian)
        {
            return EdDSA.Sign(Data, BigEndian, this.PrivateKey, this.AdditionalInfo, Hashes.ComputeSHA512Hash, this);
        }
 
        public override bool Verify(byte[] Data, byte[] PublicKey, bool BigEndian, byte[] Signature)
        {
            return EdDSA.Verify(Data, PublicKey, BigEndian, Hashes.ComputeSHA512Hash, this, Signature);
        }
 
        public override bool Verify(Stream Data, byte[] PublicKey, bool BigEndian, byte[] Signature)
        {
            return EdDSA.Verify(Data, PublicKey, BigEndian, Hashes.ComputeSHA512Hash, this, Signature);
        }
 
    }
}