3Des對每個數據塊進行了三次的DES加密算法，是DES的一個更安全的變形。比起最初的DES，3DES更為安全。
都是感覺一目了然的摘過來。
下面是加密解密的源碼。ECB模式的。
1 public class _3DESEncrypt
2 {
3
4 public static string Encrypt3DES(string a_strString, string a_strKey)
5 {
6 TripleDESCryptoServiceProvider DES = new TripleDESCryptoServiceProvider();
7 DES.Key = ASCIIEncoding.ASCII.GetBytes(System.Web.Security.FormsAuthentication.HashPasswordForStoringInConfigFile(a_strKey, "md5").Substring(0, 24));
8 DES.Mode = CipherMode.ECB;
9 ICryptoTransform DESEncrypt = DES.CreateEncryptor();
10 byte[] Buffer = ASCIIEncoding.ASCII.GetBytes(a_strString);
11 return Convert.ToBase64String(DESEncrypt.TransformFinalBlock(Buffer, 0, Buffer.Length));
12 }
13
14 public static string Decrypt3DES(string a_strString, string a_strKey)
15 {
16 TripleDESCryptoServiceProvider DES = new TripleDESCryptoServiceProvider();
17 DES.Key = ASCIIEncoding.ASCII.GetBytes(System.Web.Security.FormsAuthentication.HashPasswordForStoringInConfigFile(a_strKey, "md5").Substring(0, 24));
18 DES.Mode = CipherMode.ECB;
19 DES.Padding = System.Security.Cryptography.PaddingMode.PKCS7;
20 ICryptoTransform DESDecrypt = DES.CreateDecryptor();
21 string result = "";
22 try
23 {
24 byte[] Buffer = Convert.FromBase64String(a_strString);
25
26 result = ASCIIEncoding.ASCII.GetString(DESDecrypt.TransformFinalBlock(Buffer, 0, Buffer.Length));
27
28 //MemoryStream msDecrypt = new MemoryStream(Buffer);
29 //CryptoStream csDecrypt = new CryptoStream(msDecrypt,
30 // DES.CreateDecryptor(DES.Key, DES.IV),
31 // CryptoStreamMode.Read);
32
33 //// Create buffer to hold the decrypted data.
34 //byte[] fromEncrypt = new byte[Buffer.Length];
35
36 //// Read the decrypted data out of the crypto stream
37 //// and place it into the temporary buffer.
38 //csDecrypt.Read(fromEncrypt, 0, fromEncrypt.Length);
39 //result = System.Text.Encoding.Default.GetString(fromEncrypt);
40 }
41 catch (Exception e)
42 {
43 }
44 return result;
45
46 }
47 }
里面加解密都是在DES的基礎上實現、區別在于3Des的Key值是24位、DES而是8位。