//************************************************************************************
// 
// Copyright (c) 2007 Mohammad Sadeq Dousti
// All rights reserved.
//
// Permission is hereby granted, free of charge, to any person obtaining a
// copy of this software and associated documentation files (the
// "Software"), to deal in the Software without restriction, including
// without limitation the rights to use, copy, modify, merge, publish,
// distribute, and/or sell copies of the Software, and to permit persons
// to whom the Software is furnished to do so, provided that the above
// copyright notice(s) and this permission notice appear in all copies of
// the Software and that both the above copyright notice(s) and this
// permission notice appear in supporting documentation.
//
// THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS
// OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF
// MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT
// OF THIRD PARTY RIGHTS. IN NO EVENT SHALL THE COPYRIGHT HOLDER OR
// HOLDERS INCLUDED IN THIS NOTICE BE LIABLE FOR ANY CLAIM, OR ANY SPECIAL
// INDIRECT OR CONSEQUENTIAL DAMAGES, OR ANY DAMAGES WHATSOEVER RESULTING
// FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN ACTION OF CONTRACT,
// NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF OR IN CONNECTION
// WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
//
//************************************************************************************

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

namespace AES
{
    class Program
    {
        static int ROUND = 0;

        static void Main(string[] args)
        {
            //byte[] K = new byte[L];
            //byte[] P = new byte[L];

            byte[] K = { 0x40, 0x1F, 0x8A, 0x79, 0x3A, 0x33, 0x3C, 0x5F, 0x01, 0x5D, 0x56, 0x9B, 0xDC, 0xF0, 0x19, 0xF7 };
            byte[] P = { 0xFE, 0xDC, 0xBA, 0x98, 0x76, 0x54, 0x32, 0x10, 0x01, 0x23, 0x45, 0x67, 0x89, 0xAB, 0xCD, 0xEF };

            byte[] State = new byte[L];

            Console.WriteLine("Plaintext (Initial State):");
            printArray(P);

            Console.WriteLine("\nKey:");
            printArray(K);

            State = XOR(P, K);
            Console.WriteLine("\nState after initial AddRoundKey:");
            printArray(State);

            ROUND++;

            SubBytes(State);
            Console.WriteLine("\nState after SubBytes:");
            printArray(State);

            ShiftRows(State);
            Console.WriteLine("\nState after ShiftRows:");
            printArray(State);

            MixColumns(State);
            Console.WriteLine("\nState after MixColumns:");
            printArray(State);

            nextSubKey(K);
            State = XOR(State, K);
            Console.WriteLine("\nState after AddRoundKey:");
            printArray(State);

            ROUND++;
        }


        private static readonly byte[] Rcon ={ 0x00, 0x01, 0x02, 0x04, 0x08, 0x10, 0x20, 0x40, 0x80, 0x1B, 0x36 };

        private static void nextSubKey(byte[] K)
        {
            byte[] w = { K[13], K[14], K[15], K[12] };
            SubBytes(w);
            w[0] ^= Rcon[ROUND];

            for (int i = 0; i < 4; i++)
                K[i] ^= w[i];

            for (int i = 4; i < L; i++)
                K[i] ^= K[i - 4];

            Console.WriteLine("\nRound {0} Key:", ROUND);
            printArray(K);
        }

        private static void printArray(byte[] a)
        {
            for (int i = 0; i < L / 4; i++)
                Console.WriteLine("{0:X2} {1:X2} {2:X2} {3:X2}", a[i], a[i + 4], a[i + 8], a[i + 12]);
        }

        private static readonly byte[] A ={
            02, 03, 01, 01,
            01, 02, 03, 01,
            01, 01, 02, 03,
            03, 01, 01, 02
        };

        private static void MixColumns(byte[] State)
        {
            byte[] temp = new byte[L];

            for (int c = 0; c < L / 4; c++)
                for (int r = 0; r < 4; r++)
                    for (int t = 0; t < 4; t++)
                        temp[c * 4 + r] ^= multiply(A[r * 4 + t], State[c * 4 + t]);

            temp.CopyTo(State, 0);
        }

        const int M = 0x11B;

        private static byte multiply(byte a, byte b)
        {
            int result = 0;
            int temp = b;

            while (a > 0)
            {
                if ((a & 0x1) == 0x1)
                    result ^= temp;
                a >>= 1;
                temp <<= 1;
                if (temp >= 0x100)
                    temp ^= M;
            }

            return (byte)result;
        }

        private static readonly byte[] SHIFTS = { 
            0, 5, 10, 15,
            4, 9, 14, 3,
            8, 13, 2, 7,
            12, 1, 6, 11
        };

        private static void ShiftRows(byte[] State)
        {
            byte[] temp = (byte[])State.Clone();
            for (int i = 0; i < L; i++)
                State[i] = temp[SHIFTS[i]];
        }

        private static readonly byte[][] S = { 
            new byte[] {0x63, 0x7C, 0x77, 0x7B, 0xF2, 0x6B, 0x6F, 0xC5, 0x30, 0x01, 0x67, 0x2B, 0xFE, 0xD7, 0xAB, 0x76},
            new byte[] {0xCA, 0x82, 0xC9, 0x7D, 0xFA, 0x59, 0x47, 0xF0, 0xAD, 0xD4, 0xA2, 0xAF, 0x9C, 0xA4, 0x72, 0xC0},
            new byte[] {0xB7, 0xFD, 0x93, 0x26, 0x36, 0x3F, 0xF7, 0xCC, 0x34, 0xA5, 0xE5, 0xF1, 0x71, 0xD8, 0x31, 0x15},
            new byte[] {0x04, 0xC7, 0x23, 0xC3, 0x18, 0x96, 0x05, 0x9A, 0x07, 0x12, 0x80, 0xE2, 0xEB, 0x27, 0xB2, 0x75},
            new byte[] {0x09, 0x83, 0x2C, 0x1A, 0x1B, 0x6E, 0x5A, 0xA0, 0x52, 0x3B, 0xD6, 0xB3, 0x29, 0xE3, 0x2F, 0x84},
            new byte[] {0x53, 0xD1, 0x00, 0xED, 0x20, 0xFC, 0xB1, 0x5B, 0x6A, 0xCB, 0xBE, 0x39, 0x4A, 0x4C, 0x58, 0xCF},
            new byte[] {0xD0, 0xEF, 0xAA, 0xFB, 0x43, 0x4D, 0x33, 0x85, 0x45, 0xF9, 0x02, 0x7F, 0x50, 0x3C, 0x9F, 0xA8},
            new byte[] {0x51, 0xA3, 0x40, 0x8F, 0x92, 0x9D, 0x38, 0xF5, 0xBC, 0xB6, 0xDA, 0x21, 0x10, 0xFF, 0xF3, 0xD2},
            new byte[] {0xCD, 0x0C, 0x13, 0xEC, 0x5F, 0x97, 0x44, 0x17, 0xC4, 0xA7, 0x7E, 0x3D, 0x64, 0x5D, 0x19, 0x73},
            new byte[] {0x60, 0x81, 0x4F, 0xDC, 0x22, 0x2A, 0x90, 0x88, 0x46, 0xEE, 0xB8, 0x14, 0xDE, 0x5E, 0x0B, 0xDB},
            new byte[] {0xE0, 0x32, 0x3A, 0x0A, 0x49, 0x06, 0x24, 0x5C, 0xC2, 0xD3, 0xAC, 0x62, 0x91, 0x95, 0xE4, 0x79},
            new byte[] {0xE7, 0xC8, 0x37, 0x6D, 0x8D, 0xD5, 0x4E, 0xA9, 0x6C, 0x56, 0xF4, 0xEA, 0x65, 0x7A, 0xAE, 0x08},
            new byte[] {0xBA, 0x78, 0x25, 0x2E, 0x1C, 0xA6, 0xB4, 0xC6, 0xE8, 0xDD, 0x74, 0x1F, 0x4B, 0xBD, 0x8B, 0x8A},
            new byte[] {0x70, 0x3E, 0xB5, 0x66, 0x48, 0x03, 0xF6, 0x0E, 0x61, 0x35, 0x57, 0xB9, 0x86, 0xC1, 0x1D, 0x9E},
            new byte[] {0xE1, 0xF8, 0x98, 0x11, 0x69, 0xD9, 0x8E, 0x94, 0x9B, 0x1E, 0x87, 0xE9, 0xCE, 0x55, 0x28, 0xDF},
            new byte[] {0x8C, 0xA1, 0x89, 0x0D, 0xBF, 0xE6, 0x42, 0x68, 0x41, 0x99, 0x2D, 0x0F, 0xB0, 0x54, 0xBB, 0x16}
        };

        private const int L = 16;

        private static void SubBytes(byte[] array)
        {
            for (int i = 0; i < array.Length; i++)
                array[i] = S[array[i] / 0x10][array[i] % 0x10];
        }

        private static byte[] XOR(byte[] P, byte[] K)
        {
            int length = P.Length;
            if (K.Length != length)
                throw new ArgumentOutOfRangeException("P and K should be of the same size.");
            byte[] temp = new byte[length];
            for (int i = 0; i < length; i++)
                temp[i] = (byte)(P[i] ^ K[i]);
            return temp;
        }
    }
}