封装了一个对称加解密的类，用私钥和密钥加解密

using System;  using System.Collections.Generic;  using System.Text;  using System.IO;  using System.Security.Cryptography;    namespace CMD.EDI  {      public class EncryptHandler      {          /// <summary>          /// 加密字符串          /// </summary>          public static string Encrypt(string password, string cleartext)          {              string password2 = "Ahbool";                string cipher;              char[] key = new char[8];              if (password.Length > 8)              {                  password = password.Remove(8);              }              password.CopyTo(0, key, 0, password.Length);                char[] iv = new char[8];              if (password2.Length > 8)              {                  password2 = password2.Remove(8);              }              password2.CopyTo(0, iv, 0, password2.Length);                if (cleartext == null)              {                  return string.Empty;              }                SymmetricAlgorithm serviceProvider = new DESCryptoServiceProvider();              serviceProvider.Key = Encoding.ASCII.GetBytes(key);              serviceProvider.IV = Encoding.ASCII.GetBytes(iv);                MemoryStream memoryStream = new MemoryStream();              CryptoStream cryptoStream = new CryptoStream(memoryStream, serviceProvider.CreateEncryptor(), CryptoStreamMode.Write);              StreamWriter streamWriter = new StreamWriter(cryptoStream);                streamWriter.Write(cleartext);              streamWriter.Dispose();              cryptoStream.Dispose();                byte[] signData = memoryStream.ToArray();              memoryStream.Dispose();              serviceProvider.Clear();              cipher = Convert.ToBase64String(signData);                return cipher;          }            /// <summary>          /// 解密字符串          /// </summary>          public static string Decrypt(string password, string ciphertext)          {              string password2 = "Ahbool";                string cipher = string.Empty;                try              {                  char[] key = new char[8];                  if (password.Length > 8)                  {                      password = password.Remove(8);                  }                  password.CopyTo(0, key, 0, password.Length);                    char[] iv = new char[8];                  if (password2.Length > 8)                  {                      password2 = password2.Remove(8);                  }                  password2.CopyTo(0, iv, 0, password2.Length);                    if (ciphertext == null)                  {                      return cipher;                  }                    SymmetricAlgorithm serviceProvider = new DESCryptoServiceProvider();                  serviceProvider.Key = Encoding.ASCII.GetBytes(key);                  serviceProvider.IV = Encoding.ASCII.GetBytes(iv);                    byte[] contentArray = Convert.FromBase64String(ciphertext);                  MemoryStream memoryStream = new MemoryStream(contentArray);                  CryptoStream cryptoStream = new CryptoStream(memoryStream, serviceProvider.CreateDecryptor(), CryptoStreamMode.Read);                  StreamReader streamReader = new StreamReader(cryptoStream);                    cipher = streamReader.ReadToEnd();                    streamReader.Dispose();                  cryptoStream.Dispose();                  memoryStream.Dispose();                  serviceProvider.Clear();                }              catch (Exception ex)              {                  throw new SystemException("密钥错误,数据包解密失败.");              }                return cipher;          }          }  }