.Net框架由于拥有CLR提供的丰富库支持，只需很少的代码即可实现先前使用C等旧式语言很难实现的加密算法。本类实现一些常用机密算法，供参考。其中MD5算法返回Int的ToString字串。返回数字字母型结果的算法参见之前Blog文章。

using System;
using System.IO;
using System.Data;
using System.Text;
using System.Diagnostics;
using System.Security;
using System.Security.Cryptography;

namespace com.Quickline.Encrypt
{
 /// <summary>
 /// 类名：HashEncrypt
 /// 作用：对传入的字符串进行Hash运算，返回通过Hash算法加密过的字串。
 /// 属性：［无］
 /// 构造函数额参数：
 /// IsReturnNum:是否返回为加密后字符的Byte代码
 /// IsCaseSensitive：是否区分大小写。
 /// 方法：此类提供MD5，SHA1，SHA256，SHA512等四种算法，加密字串的长
度依次增大。
 /// </summary>
 public class HashEncrypt
 {
  //private string strIN;
  private bool isReturnNum;
  private bool isCaseSensitive;
  
  public HashEncrypt(bool IsCaseSensitive,bool IsReturnNum)
  {
   this.isReturnNum = IsReturnNum;
   this.isCaseSensitive = IsCaseSensitive;
  }
  
  
  private string getstrIN(string strIN)
  {
   //string strIN = strIN;
   if (strIN.Length == 0)
   {
    strIN = \"~NULL~\";
   }
   if (isCaseSensitive == false)
   {
    strIN = strIN.ToUpper();
   }
   return strIN;
  }
  public string MD5Encrypt(string strIN)
  {
   //string strIN = getstrIN(strIN);
   byte[] tmpByte;
   MD5 md5 = new MD5CryptoServiceProvider();
   tmpByte =
md5.ComputeHash(GetKeyByteArray(getstrIN(strIN)));
   md5.Clear();

   return GetStringValue(tmpByte);

  }
  
  public string SHA1Encrypt(string strIN)
  {
   //string strIN = getstrIN(strIN);
   byte[] tmpByte;
   SHA1 sha1 = new SHA1CryptoServiceProvider();

   tmpByte = sha1.ComputeHash(GetKeyByteArray(strIN));
   sha1.Clear();

   return GetStringValue(tmpByte);

  }

  public string SHA256Encrypt(string strIN)
  {
   //string strIN = getstrIN(strIN);
   byte[] tmpByte;
   SHA256 sha256 = new SHA256Managed();

   tmpByte =
sha256.ComputeHash(GetKeyByteArray(strIN));
   sha256.Clear();

   return GetStringValue(tmpByte);

  }

  public string SHA512Encrypt(string strIN)
  {
   //string strIN = getstrIN(strIN);
   byte[] tmpByte;
   SHA512 sha512 = new SHA512Managed();

   tmpByte =
sha512.ComputeHash(GetKeyByteArray(strIN));
   sha512.Clear();

   return GetStringValue(tmpByte);

  }
  
  /// <summary>
  /// 使用DES加密（Added by niehl 2005-4-6）
  /// </summary>
  /// <param name=\"originalValue\">待加密的字符串</param>
  /// <param name=\"key\">密钥(最大长度8)</param>
  /// <param name=\"IV\">初始化向量(最大长度8)</param>
  /// <returns>加密后的字符串</returns>
  public string DESEncrypt(string originalValue,string key,string IV)
  {
   //将key和IV处理成8个字符
   key += \"12345678\";
   IV += \"12345678\";
   key = key.Substring(0,8);
   IV = IV.Substring(0,8);

   SymmetricAlgorithm sa;
   ICryptoTransform ct;
   MemoryStream ms;
   CryptoStream cs;
   byte[] byt;

   sa = new DESCryptoServiceProvider();
   sa.Key = Encoding.UTF8.GetBytes(key);
   sa.IV = Encoding.UTF8.GetBytes(IV);
   ct = sa.CreateEncryptor();

   byt = Encoding.UTF8.GetBytes(originalValue);

   ms = new MemoryStream();
   cs = new CryptoStream(ms, ct,
CryptoStreamMode.Write);
   cs.Write(byt, 0, byt.Length);
   cs.FlushFinalBlock();

   cs.Close();

   return Convert.ToBase64String(ms.ToArray());

  }

  public string DESEncrypt(string originalValue,string key)
  {
   return DESEncrypt(originalValue,key,key);
  }

  /// <summary>
  /// 使用DES解密（Added by niehl 2005-4-6）
  /// </summary>
  /// <param name=\"encryptedValue\">待解密的字符串</param>
  /// <param name=\"key\">密钥(最大长度8)</param>
  /// <param name=\"IV\">m初始化向量(最大长度8)</param>
  /// <returns>解密后的字符串</returns>
  public string DESDecrypt(string encryptedValue,string key,string IV)
  {
   //将key和IV处理成8个字符
   key += \"12345678\";
   IV += \"12345678\";
   key = key.Substring(0,8);
   IV = IV.Substring(0,8);

   SymmetricAlgorithm sa;
   ICryptoTransform ct;
   MemoryStream ms;
   CryptoStream cs;
   byte[] byt;

   sa = new DESCryptoServiceProvider();
   sa.Key = Encoding.UTF8.GetBytes(key);
   sa.IV = Encoding.UTF8.GetBytes(IV);
   ct = sa.CreateDecryptor();

   byt = Convert.FromBase64String(encryptedValue);

   ms = new MemoryStream();
   cs = new CryptoStream(ms, ct,
CryptoStreamMode.Write);
   cs.Write(byt, 0, byt.Length);
   cs.FlushFinalBlock();

   cs.Close();

   return Encoding.UTF8.GetString(ms.ToArray());

  }

  public string DESDecrypt(string encryptedValue,string key)
  {
   return DESDecrypt(encryptedValue,key,key);
  }

  private string GetStringValue(byte[] Byte)
  {
   string tmpString = \"\";

   if (this.isReturnNum == false)
   {
    ASCIIEncoding Asc = new ASCIIEncoding();
    tmpString = Asc.GetString(Byte);
   }
   else
   {
    int iCounter;

    for
(iCounter=0;iCounter<Byte.Length;iCounter++)
    {
     tmpString = tmpString +
Byte[iCounter].ToString();
    }
    
   }
   
   return tmpString;
  }

  private byte[] GetKeyByteArray(string strKey)
  {

   ASCIIEncoding Asc = new ASCIIEncoding();
   
   int tmpStrLen = strKey.Length;
   byte[] tmpByte = new byte[tmpStrLen-1];

   tmpByte = Asc.GetBytes(strKey);

   return tmpByte;

  }

 }
}