DES加密解密

 密鈅長度有規定，密文長度應該是無限定。註釋中寫的長度是爲了滿足以下需求：密文長度固定。

 1     ///<summary>
 2     ///DES 加密解密
 3     ///Rex Rao @2011-5-13
 4     ///</summary>
 5     public static class DES
 6     {
 7         ///<summary>
 8         /// DES加密
 9         ///</summary>
10         ///<param name="content">8-15bytes明文</param>
11         ///<param name="key">8bytes密鈅</param>
12         ///<returns>32bytes密文</returns>
13         public static string DESEncrypt(string content, string key)
14         {
15             byte[] data = Encoding.ASCII.GetBytes(content);
16             DESCryptoServiceProvider DES = new DESCryptoServiceProvider();
17             DES.Key = ASCIIEncoding.ASCII.GetBytes(key);
18             DES.IV = ASCIIEncoding.ASCII.GetBytes(key);
19             MemoryStream ms = new MemoryStream();  //內存流。
20             CryptoStream cs = new CryptoStream(ms, DES.CreateEncryptor(), CryptoStreamMode.Write);//內存流創建為加密轉換流
21             cs.Write(data, 0, data.Length);
22             cs.FlushFinalBlock();  //用缓冲区的当前状态更新基础数据源或储存库，随后清除缓
23             StringBuilder ret = new StringBuilder();
24             foreach (byte b in ms.ToArray())
25             {
26                 ret.AppendFormat("{0:X2}", b);
27             }
28             return ret.ToString();
29         }
30 
31         ///<summary>
32         /// DES解密
33         ///</summary>
34         ///<param name="content">32bytes密文</param>
35         ///<param name="key">8bytes密鈅</param>
36         ///<returns>8-15bytes明文</returns>
37         public static string DESDecrypt(string content, string key)
38         {
39             DESCryptoServiceProvider des = new DESCryptoServiceProvider();
40 
41             //Put  the  input  string  into  the  byte  array  
42             byte[] inputByteArray = new byte[content.Length / 2];
43             for (int x = 0; x < content.Length; x += 2)
44             {
45                 int i = Convert.ToInt32(content.Substring(x, 2), 16);
46                 inputByteArray[x / 2] = (byte)i;
47             }
48 
49             des.Key = ASCIIEncoding.ASCII.GetBytes(key);
50             des.IV = ASCIIEncoding.ASCII.GetBytes(key);
51             MemoryStream ms = new MemoryStream();
52             CryptoStream cs = new CryptoStream(ms, des.CreateDecryptor(), CryptoStreamMode.Write);
53             //Flush  the  data  through  the  crypto  stream  into  the  memory  stream  
54             cs.Write(inputByteArray, 0, inputByteArray.Length);
55             cs.FlushFinalBlock();
56 
57             //Get  the  decrypted  data  back  from  the  memory  stream  
58             //建立StringBuild对象，CreateDecrypt使用的是流对象，必须把解密后的文本变成流对象  
59             StringBuilder ret = new StringBuilder();
60 
61             return System.Text.Encoding.UTF8.GetString(ms.ToArray());
62         }
63     }