EllipticCurveEndpoint.cs

using System;
using System.IO;
using Waher.Runtime.Cache;
using Waher.Security;
using Waher.Security.EllipticCurves;
 
namespace Waher.Networking.XMPP.P2P.E2E
{
    public abstract class EllipticCurveEndpoint : E2eEndpoint
    {
        private static readonly Cache<string, byte[]> sharedSecrets = new Cache<string, byte[]>(int.MaxValue, TimeSpan.MaxValue, TimeSpan.FromDays(1), true);
 
        protected readonly byte[] publicKey;
        private readonly EllipticCurve curve;
        private readonly bool hasPrivateKey;
        private readonly string publicKeyBase64;
 
        public EllipticCurveEndpoint(EllipticCurve Curve, IE2eSymmetricCipher DefaultSymmetricCipher)
            : base(DefaultSymmetricCipher)
        {
            this.curve = Curve;
            this.publicKey = Curve.PublicKey;
            this.hasPrivateKey = true;
            this.publicKeyBase64 = Convert.ToBase64String(this.publicKey);
        }
 
        public EllipticCurveEndpoint(byte[] PublicKey, EllipticCurve ReferenceCurve, IE2eSymmetricCipher DefaultSymmetricCipher)
            : base(DefaultSymmetricCipher)
        {
            this.publicKey = PublicKey;
            this.curve = ReferenceCurve;
            this.hasPrivateKey = false;
            this.publicKeyBase64 = Convert.ToBase64String(this.publicKey);
        }
 
        public bool HasPrivateKey => this.hasPrivateKey;
 
        public override byte[] PublicKey => this.publicKey;
 
        public override string PublicKeyBase64 => this.publicKeyBase64;
 
        public string CurveName => this.curve.CurveName;
 
        public EllipticCurve Curve => this.curve;
 
        public EllipticCurve PrevCurve => (this.Previous as EllipticCurveEndpoint)?.Curve;
 
        public override byte[] GetSharedSecretForEncryption(IE2eEndpoint RemoteEndpoint,
            IE2eSymmetricCipher Cipher, out byte[] CipherText)
        {
            CipherText = null;
            return GetSharedKey(this, RemoteEndpoint);
        }
 
        public override byte[] GetSharedSecretForDecryption(IE2eEndpoint RemoteEndpoint,
            byte[] CipherText)
        {
            return GetSharedKey(this, RemoteEndpoint);
        }
 
        public override bool SharedSecretUseCipherText => false;
 
        public static byte[] GetSharedKey(EllipticCurveEndpoint LocalKey, IE2eEndpoint RemoteKey)
        {
            string Key = LocalKey.PublicKeyBase64 + ";" + RemoteKey.PublicKeyBase64;
 
            if (sharedSecrets.TryGetValue(Key, out byte[] SharedKey))
                SharedKey = (byte[])SharedKey.Clone();
            else
            {
                SharedKey = LocalKey.curve.GetSharedKey(RemoteKey.PublicKey, false, Hashes.ComputeSHA256Hash);
                sharedSecrets[Key] = (byte[])SharedKey.Clone();
            }
 
            return SharedKey;
        }
 
        public override byte[] Sign(byte[] Data)
        {
            if (!this.hasPrivateKey)
                throw new InvalidOperationException("Signing requires private key.");
 
            byte[] Signature = this.curve.Sign(Data, false);
 
            return Signature;
        }
 
        public override byte[] Sign(Stream Data)
        {
            if (!this.hasPrivateKey)
                throw new InvalidOperationException("Signing requires private key.");
 
            byte[] Signature = this.curve.Sign(Data, false);
 
            return Signature;
        }
 
        public bool Verify(byte[] Data, byte[] PublicKey, byte[] Signature)
        {
            return this.curve.Verify(Data, PublicKey, false, Signature);
        }
 
        public bool Verify(Stream Data, byte[] PublicKey, byte[] Signature)
        {
            return this.curve.Verify(Data, PublicKey, false, Signature);
        }
 
        public override bool Verify(byte[] Data, byte[] Signature)
        {
            return this.Verify(Data, this.publicKey, Signature);
        }
 
        public override bool Verify(Stream Data, byte[] Signature)
        {
            return this.Verify(Data, this.publicKey, Signature);
        }
 
        public override bool Equals(object obj)
        {
            return obj is EllipticCurveEndpoint EcEndpoint &&
                this.curve.CurveName.Equals(EcEndpoint.curve.CurveName) &&
                this.publicKeyBase64.Equals(EcEndpoint.publicKeyBase64);
        }
 
        public override int GetHashCode()
        {
            int Result = this.curve.CurveName.GetHashCode();
            Result ^= Result << 5 ^ this.publicKeyBase64.GetHashCode();
 
            return Result;
        }
 
    }
}