using System;

using System.Linq;

namespace HexXor

{

    public class HexString

    {

        private byte[] _data;

        public HexString(string data)

        {

            if ((data.Length & 1)!= 0) throw new ArgumentException("Hex string must have an even number of digits.");

            _data = Enumerable.Range(0, data.Length)

                .Where(x => x % 2 == 0)

                .Select(x => Convert.ToByte(data.Substring(x, 2), 16))

                .ToArray();

        }

        public HexString(byte[] data)

        {

            _data = data;

        }

        public override string ToString()

        {

            string hex = BitConverter.ToString(_data);

            return hex.Replace("-","");

        }

        static public HexString operator ^(HexString LHS, HexString RHS)

        {

            return new HexString

                (

                    LHS._data.Zip

                        ( 

                            RHS._data, 

                            (a, b) => (byte)(a ^ b)

                        )

                    .ToArray()

                );

        } 

    }

    public class Program

    {

        static public void Main()

        {

            HexString bdk1 = new HexString("8D10DA193E98524379264ADFFD043632");

            HexString bdk2 = new HexString("8C339F7EB7339FAC87FAF0478B500422");

            const string expected = "0123456789ABCDEFFEDCBA9876543210";

            HexString actual = bdk1 ^ bdk2;

            Console.WriteLine("Expected: " + expected);

            Console.WriteLine("Actual  : " + actual);

            Console.ReadLine(); 

        }

    }

}