?//AES算法過程與書中3.6.1所述相同，為了便于理解，變量名字也一樣。
using System;

namespace Aes算法
{
    public class Aes  
    {   
       
        private byte[] key;     // 存儲種子密鑰
        private byte[,] Sbox;   // S盒
        private byte[,] iSbox;  // 逆向S盒
        private byte[,] w;      // 存儲擴展密鑰 
        private byte[,] Rcon;   // Round constants.
        private byte[,] State;  // State矩陣

        public Aes(byte[] keyBytes) //AES結構
        {
            this.key = new byte[32]; 
            keyBytes.CopyTo(this.key, 0);

            構造Sbox矩陣();
            構造Sbox逆矩陣();
            構造Rcon數組();//擴展密鑰用到的Rcon
            KeyExpansion();  //擴展種子密鑰存儲在w數組內

        }  

        public void Cipher(byte[] input, byte[] output)  //加密算法
        {
            
            this.State = new byte[4, 4];  

                for (int i = 0; i <16; i ++)//輸入明文
                {
                    this.State[i % 4, i / 4] = input[i];
                }

            AddRoundKey(0);

            for (int round = 1; round <= 13 ; round ++)  
            {
                SubBytes();
                ShiftRows();
                MixColumn();
                AddRoundKey(round);
            }  
            SubBytes();
            ShiftRows();
            AddRoundKey(14);

            
            for (int i = 0; i <16; i ++)//輸出密文
            {
                output[i] = this.State[i % 4, i / 4];
            }

        }  

        public void InvCipher(byte[] input, byte[] output) //解密算法
        {
          
            this.State = new byte[4, 4];  
            for (int i = 0; i < 16; i ++)//輸入密文
            {
                this.State[i % 4, i / 4] = input[i];
            }

            AddRoundKey(14);

            for (int round = 13; round >= 1; round --)  
            {
                逆ShiftRows();
                逆SubBytes();
                AddRoundKey(round);
                逆MixColumn();
            } 

            逆ShiftRows();
            逆SubBytes();
            AddRoundKey(0);

       
            for (int i = 0; i < 16; i ++)//輸出解密文
            {
                output[i] = this.State[i % 4, i / 4];
            }

        }  

       

        private void 構造Sbox矩陣()
        {
            this.Sbox = new byte[16, 16] {  //s盒代換矩陣
    
            {0x63, 0x7c, 0x77, 0x7b, 0xf2, 0x6b, 0x6f, 0xc5, 0x30, 0x01, 0x67, 0x2b, 0xfe, 0xd7, 0xab, 0x76},
            {0xca, 0x82, 0xc9, 0x7d, 0xfa, 0x59, 0x47, 0xf0, 0xad, 0xd4, 0xa2, 0xaf, 0x9c, 0xa4, 0x72, 0xc0},
            {0xb7, 0xfd, 0x93, 0x26, 0x36, 0x3f, 0xf7, 0xcc, 0x34, 0xa5, 0xe5, 0xf1, 0x71, 0xd8, 0x31, 0x15},
            {0x04, 0xc7, 0x23, 0xc3, 0x18, 0x96, 0x05, 0x9a, 0x07, 0x12, 0x80, 0xe2, 0xeb, 0x27, 0xb2, 0x75},
            {0x09, 0x83, 0x2c, 0x1a, 0x1b, 0x6e, 0x5a, 0xa0, 0x52, 0x3b, 0xd6, 0xb3, 0x29, 0xe3, 0x2f, 0x84},
            {0x53, 0xd1, 0x00, 0xed, 0x20, 0xfc, 0xb1, 0x5b, 0x6a, 0xcb, 0xbe, 0x39, 0x4a, 0x4c, 0x58, 0xcf},
            {0xd0, 0xef, 0xaa, 0xfb, 0x43, 0x4d, 0x33, 0x85, 0x45, 0xf9, 0x02, 0x7f, 0x50, 0x3c, 0x9f, 0xa8},
            {0x51, 0xa3, 0x40, 0x8f, 0x92, 0x9d, 0x38, 0xf5, 0xbc, 0xb6, 0xda, 0x21, 0x10, 0xff, 0xf3, 0xd2},
            {0xcd, 0x0c, 0x13, 0xec, 0x5f, 0x97, 0x44, 0x17, 0xc4, 0xa7, 0x7e, 0x3d, 0x64, 0x5d, 0x19, 0x73},
            {0x60, 0x81, 0x4f, 0xdc, 0x22, 0x2a, 0x90, 0x88, 0x46, 0xee, 0xb8, 0x14, 0xde, 0x5e, 0x0b, 0xdb},
            {0xe0, 0x32, 0x3a, 0x0a, 0x49, 0x06, 0x24, 0x5c, 0xc2, 0xd3, 0xac, 0x62, 0x91, 0x95, 0xe4, 0x79},
            {0xe7, 0xc8, 0x37, 0x6d, 0x8d, 0xd5, 0x4e, 0xa9, 0x6c, 0x56, 0xf4, 0xea, 0x65, 0x7a, 0xae, 0x08},
            {0xba, 0x78, 0x25, 0x2e, 0x1c, 0xa6, 0xb4, 0xc6, 0xe8, 0xdd, 0x74, 0x1f, 0x4b, 0xbd, 0x8b, 0x8a},
            {0x70, 0x3e, 0xb5, 0x66, 0x48, 0x03, 0xf6, 0x0e, 0x61, 0x35, 0x57, 0xb9, 0x86, 0xc1, 0x1d, 0x9e},
            {0xe1, 0xf8, 0x98, 0x11, 0x69, 0xd9, 0x8e, 0x94, 0x9b, 0x1e, 0x87, 0xe9, 0xce, 0x55, 0x28, 0xdf},
            {0x8c, 0xa1, 0x89, 0x0d, 0xbf, 0xe6, 0x42, 0x68, 0x41, 0x99, 0x2d, 0x0f, 0xb0, 0x54, 0xbb, 0x16} };

        } 

        private void 構造Sbox逆矩陣()
        {
            this.iSbox = new byte[16, 16] {  //逆矩陣
           
              {0x52, 0x09, 0x6a, 0xd5, 0x30, 0x36, 0xa5, 0x38, 0xbf, 0x40, 0xa3, 0x9e, 0x81, 0xf3, 0xd7, 0xfb},
              {0x7c, 0xe3, 0x39, 0x82, 0x9b, 0x2f, 0xff, 0x87, 0x34, 0x8e, 0x43, 0x44, 0xc4, 0xde, 0xe9, 0xcb},
              {0x54, 0x7b, 0x94, 0x32, 0xa6, 0xc2, 0x23, 0x3d, 0xee, 0x4c, 0x95, 0x0b, 0x42, 0xfa, 0xc3, 0x4e},
              {0x08, 0x2e, 0xa1, 0x66, 0x28, 0xd9, 0x24, 0xb2, 0x76, 0x5b, 0xa2, 0x49, 0x6d, 0x8b, 0xd1, 0x25},
              {0x72, 0xf8, 0xf6, 0x64, 0x86, 0x68, 0x98, 0x16, 0xd4, 0xa4, 0x5c, 0xcc, 0x5d, 0x65, 0xb6, 0x92},
              {0x6c, 0x70, 0x48, 0x50, 0xfd, 0xed, 0xb9, 0xda, 0x5e, 0x15, 0x46, 0x57, 0xa7, 0x8d, 0x9d, 0x84},
              {0x90, 0xd8, 0xab, 0x00, 0x8c, 0xbc, 0xd3, 0x0a, 0xf7, 0xe4, 0x58, 0x05, 0xb8, 0xb3, 0x45, 0x06},
              {0xd0, 0x2c, 0x1e, 0x8f, 0xca, 0x3f, 0x0f, 0x02, 0xc1, 0xaf, 0xbd, 0x03, 0x01, 0x13, 0x8a, 0x6b},
              {0x3a, 0x91, 0x11, 0x41, 0x4f, 0x67, 0xdc, 0xea, 0x97, 0xf2, 0xcf, 0xce, 0xf0, 0xb4, 0xe6, 0x73},
              {0x96, 0xac, 0x74, 0x22, 0xe7, 0xad, 0x35, 0x85, 0xe2, 0xf9, 0x37, 0xe8, 0x1c, 0x75, 0xdf, 0x6e},
              {0x47, 0xf1, 0x1a, 0x71, 0x1d, 0x29, 0xc5, 0x89, 0x6f, 0xb7, 0x62, 0x0e, 0xaa, 0x18, 0xbe, 0x1b},
              {0xfc, 0x56, 0x3e, 0x4b, 0xc6, 0xd2, 0x79, 0x20, 0x9a, 0xdb, 0xc0, 0xfe, 0x78, 0xcd, 0x5a, 0xf4},
              {0x1f, 0xdd, 0xa8, 0x33, 0x88, 0x07, 0xc7, 0x31, 0xb1, 0x12, 0x10, 0x59, 0x27, 0x80, 0xec, 0x5f},
              {0x60, 0x51, 0x7f, 0xa9, 0x19, 0xb5, 0x4a, 0x0d, 0x2d, 0xe5, 0x7a, 0x9f, 0x93, 0xc9, 0x9c, 0xef},
              {0xa0, 0xe0, 0x3b, 0x4d, 0xae, 0x2a, 0xf5, 0xb0, 0xc8, 0xeb, 0xbb, 0x3c, 0x83, 0x53, 0x99, 0x61},
              {0x17, 0x2b, 0x04, 0x7e, 0xba, 0x77, 0xd6, 0x26, 0xe1, 0x69, 0x14, 0x63, 0x55, 0x21, 0x0c, 0x7d} };
        } 

        private void 構造Rcon數組()
        {
            this.Rcon = new byte[11, 4] {  {0x00, 0x00, 0x00, 0x00},  
                                           {0x01, 0x00, 0x00, 0x00},
                                           {0x02, 0x00, 0x00, 0x00},
                                           {0x04, 0x00, 0x00, 0x00},
                                           {0x08, 0x00, 0x00, 0x00},
                                           {0x10, 0x00, 0x00, 0x00},
                                           {0x20, 0x00, 0x00, 0x00},
                                           {0x40, 0x00, 0x00, 0x00},
                                           {0x80, 0x00, 0x00, 0x00},
                                           {0x1b, 0x00, 0x00, 0x00},
                                           {0x36, 0x00, 0x00, 0x00} };
        }  

        private void AddRoundKey(int round)//addRoundKey操作
        {

            for (int r = 0; r < 4; r ++)
            {
                for (int c = 0; c < 4; c ++)
                {
                    this.State[r, c] = (byte)((int)this.State[r, c] ^ (int)w[(round * 4) + c, r]);
                }
            }
        } 

        private void SubBytes()//subBytes操作,書中算法3.4
        {
            for (int r = 0; r < 4; r ++)
            {
                for (int c = 0; c < 4; c ++)
                {
                    this.State[r, c] = this.Sbox[(this.State[r, c] >> 4), (this.State[r, c] & 0x0f)];
                }
            }
        }  

        private void 逆SubBytes()//對應于SubBytes的逆操作
        {
            for (int r = 0; r < 4; r ++)
            {
                for (int c = 0; c < 4; c ++)
                {
                    this.State[r, c] = this.iSbox[(this.State[r, c] >> 4), (this.State[r, c] & 0x0f)];
                }
            }
        }  

        private void ShiftRows()//對State的ShiftRows操作
        {
            byte[,] temp = new byte[4, 4];
            for (int r = 0; r < 4; r ++)  //將State復制給數組temp
            {
                for (int c = 0; c < 4; c ++)
                {