?/*
 * 數據加密標準(DES)的C#實現(3)
 * 將BitConverter.ToString的結果轉回byte[]
 * 
 * 采用隨機的密鑰Key和初始化向量IV加密
 * 使用隨機密碼的好處：系統不會產生弱密鑰
 * 備注：本例與《數據加密標準(DES)的C#實現(2)》本質相同，只是采用BitConverter.ToString
 * 輸出密文、密鑰和初始化向量，而不是采用Base64編碼格式
 * 
 * 
 * 夏春濤 Email:xChuntao@163.com 
 * Blog:http://bluesky521.cnblogs.com
 * 運行環境：.net2.0 framework
 */

/* 
 * 關于DES加密中的初始化向量IV：
 * 對于給定的密鑰 k，不使用初始化向量的簡單塊密碼將同一個純文本輸入塊加密為
 * 同一個密碼文本輸出塊。如果您的純文本流中有重復塊，則您的密碼文本流中也會
 * 有重復塊。如果未經授權的用戶知道了您的純文本塊結構的任何信息，他們就可以
 * 利用該信息來解密已知的密碼文本塊，并有可能重新獲得您的密鑰。為了防止這個
 * 問題，前一個塊中的信息被混合到下一個塊的加密過程中。這樣一來，兩個相同的
 * 純文本塊的輸出就變得不一樣了。由于此技術使用前一個塊加密下一個塊，因此需
 * 要初始化向量來加密數據的第一個塊。 
 */

using System;
using System.Collections.Generic;
using System.Text;
using System.Security.Cryptography;
using System.IO;

namespace DES_App3
{
    class Program
    {
        static void Main(string[] args)
        {
            string str_plain_text = "How are you?";
            Console.WriteLine("原文：" + str_plain_text);

            string KEY_64 = ""; 
            string IV_64 = "";  

            string str_cypher_text = DES_Encrypt(str_plain_text, out KEY_64, out IV_64);
            Console.WriteLine("密文：" + str_cypher_text);
            
            Console.WriteLine("解密：" + DES_Decrypt(str_cypher_text, KEY_64, IV_64));

            Console.WriteLine("本次密鑰：" + KEY_64);
            Console.WriteLine("本次初始化向量：" + IV_64);
            Console.WriteLine();

            //-------------------------------

            str_cypher_text = DES_Encrypt(str_plain_text, out KEY_64, out IV_64, false);
            Console.WriteLine("密文：" + str_cypher_text);

            Console.WriteLine("解密：" + DES_Decrypt(str_cypher_text, KEY_64, IV_64));

            Console.WriteLine("本次密鑰：" + KEY_64);
            Console.WriteLine("本次初始化向量：" + IV_64);
            Console.WriteLine();
            
        }

        //將BitConverter.ToString字符串,如"98-ED-0S-9A"，還原轉換為byte[]
        static public byte[] BitStr_ToBytes(string bit_str)
        {
            string[] arrSplit = bit_str.Split('-');
            byte[] byteTemp = new byte[arrSplit.Length];
            for (int i = 0; i < byteTemp.Length; i++)
            {
                byteTemp[i] = byte.Parse(arrSplit[i], System.Globalization.NumberStyles.AllowHexSpecifier);

            }

            return byteTemp;
        }

        //將BitConverter.ToString字符串(不含'-'),如"98ED0S9A"，還原轉換為byte[]
        static public byte[] BitStr_ToBytes2(string bit_str)
        {
            int n = bit_str.Length / 2 - 1;
            for (int i = n; i > 0; i--)
            {
                bit_str = bit_str.Insert(i * 2, "-");
            }

            return BitStr_ToBytes(bit_str);
        }

        //----
        #region DES加密/解密
        /// <summary>
        /// DES加密
        /// </summary>
        /// <param name="str_plain_text">明文</param>
        /// <param name="str_des_key">密鑰，8個字符（64bit）</param>
        /// <param name="str_des_iv">初始向量，8個字符（64bit）</param>
        /// <param name="hasSubSign">輸出密文、str_des_key和str_des_iv時，是否保留BitConvert.ToString中的減號</param>
        /// <returns>密文</returns>
        static public string DES_Encrypt(string str_plain_text, out string str_des_key, out string str_des_iv, bool hasSubSign)
        {
            string str_cypher_text = "";

            DESCryptoServiceProvider cryptoProvider = new DESCryptoServiceProvider();

            MemoryStream ms = new MemoryStream();
            CryptoStream cst = new CryptoStream(ms, cryptoProvider.CreateEncryptor(), CryptoStreamMode.Write);

            StreamWriter sw = new StreamWriter(cst);
            sw.Write(str_plain_text);
            sw.Flush();
            cst.FlushFinalBlock();
            sw.Flush();
            //-----
            str_cypher_text = BitConverter.ToString(ms.GetBuffer(),0,(int)ms.Length);//**
            str_des_key = BitConverter.ToString(cryptoProvider.Key);//**
            str_des_iv = BitConverter.ToString(cryptoProvider.IV);  //**

            if (!hasSubSign)
            {
                str_cypher_text = str_cypher_text.Replace("-", "");
                str_des_key = str_des_key.Replace("-","");
                str_des_iv = str_des_iv.Replace("-","");
            }

            return str_cypher_text;
        }

        static public string DES_Encrypt(string str_plain_text, out string str_des_key, out string str_des_iv)
        {
            return DES_Encrypt(str_plain_text, out str_des_key, out str_des_iv, true);
        }

        /// <summary>
        /// DES解密
        /// </summary>
        /// <param name="str_cypher_text">密文</param>
        /// <param name="str_des_key">密鑰，8個字符（64bit）</param>
        /// <param name="str_des_iv">初始向量，8個字符（64bit）</param>
        /// <returns>明文</returns>
        static public string DES_Decrypt(string str_cypher_text, string str_des_key, string str_des_iv)
        {
            byte[] byKey;
            byte[] byIV;
            byte[] byEnc;
            try
            {
                if (str_cypher_text.IndexOf('-') > 0 && str_des_key.IndexOf('-') > 0 && str_des_iv.IndexOf('-') > 0)//有"-"號
                {
                    byKey = BitStr_ToBytes(str_des_key);
                    byIV = BitStr_ToBytes(str_des_iv);
                    byEnc = BitStr_ToBytes(str_cypher_text);
                }
                else//無"-"號
                {
                    byKey = BitStr_ToBytes2(str_des_key);
                    byIV = BitStr_ToBytes2(str_des_iv);
                    byEnc = BitStr_ToBytes2(str_cypher_text);
                }
            }
            catch
            {
                return null;
            }

            DESCryptoServiceProvider cryptoProvider = new DESCryptoServiceProvider();
            MemoryStream ms = new MemoryStream(byEnc);
            CryptoStream cst = new CryptoStream(ms, cryptoProvider.CreateDecryptor(byKey, byIV), CryptoStreamMode.Read);
            StreamReader sr = new StreamReader(cst);
            string str_plain_text = sr.ReadToEnd();


            return str_plain_text;
        }
        #endregion
    }
}