Cptr427DesProgrammingLecture

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using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;

namespace DES
{
    class DesUtility
    {

        /// <summary>
        /// We are using a 1's based numbering system from the right
        /// </summary>
        /// <param name="input">64-bit unsigned long data</param>
        /// <param name="posIn">a value between 1 and 64</param>
        /// <param name="posOut">a value between 1 and 64</param>
        /// <returns></returns>
        public static ulong shiftBit(ulong input, int posIn, int posOut)
        {
            ulong output = 0;
            input >>= posIn - 1;
            input &= 1;
            input <<= posOut - 1;
            output |= input;

            return output;
        }

        public static ulong reverseNumber(ulong input)
        {
            ulong output = 0;
            for (int i = 1; i <= 64; i++)
            {
                ulong temp = shiftBit(input, i, 65 - i);
                output |= temp;
            }
            return output;
        }

        /// <summary>
        /// Take the output position to be i and int input position to be 
        /// permutation[i] to create the output ulong value.
        /// </summary>
        /// <param name="input"></param>
        /// <param name="permutation"></param>
        /// <returns></returns>
        public static ulong Permutation(ulong input, int[] permutation)
        {
            ulong output = 0;
            for (int i = 0; i < permutation.Length; i++)
            {
                output |= shiftBit(input, permutation[i], i + 1);
            }
            return output;

        }

    }
}