ECDHx -TizzyT

    public class ECDHx : IDisposable
    {
        public enum ECDiffieHellmanModes
        {
            MD5,
            SHA1,
            SHA256,
            SHA384,
            SHA512
        }

        internal readonly ECDiffieHellmanCng ecdh;

        public byte[] PublicKey { get; }

        public ECDHx(ECDiffieHellmanModes Mode)
        {
            ecdh = new ECDiffieHellmanCng();
            ecdh.KeyDerivationFunction = ECDiffieHellmanKeyDerivationFunction.Hash;
            switch (Mode)
            {
                case ECDiffieHellmanModes.MD5:
                    ecdh.HashAlgorithm = CngAlgorithm.MD5;
                    break;
                case ECDiffieHellmanModes.SHA1:
                    ecdh.HashAlgorithm = CngAlgorithm.Sha1;
                    break;
                case ECDiffieHellmanModes.SHA256:
                    ecdh.HashAlgorithm = CngAlgorithm.Sha256;
                    break;
                case ECDiffieHellmanModes.SHA384:
                    ecdh.HashAlgorithm = CngAlgorithm.Sha384;
                    break;
                case ECDiffieHellmanModes.SHA512:
                    ecdh.HashAlgorithm = CngAlgorithm.Sha512;
                    break;
            }
            PublicKey = ecdh.PublicKey.ToByteArray();
        }

        public byte[] DeriveSharedKey(byte[] PublicKey)
        {
            byte[] SharedKey = ecdh.DeriveKeyMaterial(ECDiffieHellmanCngPublicKey.FromByteArray(PublicKey, CngKeyBlobFormat.EccPublicBlob));
            return SharedKey;
        }

        public void Dispose() => ecdh.Dispose();
    }