这个类是我在网上参考了几个文档总结出来的，测试过可以直接用，后面有一段ＭＤ５的，应该独立成一个类的，我懒，所以测试的时候就写到一个文件里了，感觉还是满实用的，如果有什么机密文件，就用这个东西处理一下，将来要看的时候再反过来处理一下，只是你不要忘记了密码就对了，如果你跟我一样懒，你直接把下面的代码拷贝下来直接用吧。
using System;
using System.IO;
using System.Text;
using System.Security.Cryptography;
using System.Web;

namespace Test.Com
{
/// <summary>
/// DESEncryptor 的摘要说明。
/// </summary>
public class DESEncryptor
{
#region 私有成员
/// <summary>
/// 输入字符串
/// </summary>
private string inputString=null;
/// <summary>
/// 输出字符串
/// </summary>
private string outString=null;
/// <summary>
/// 输入文件路径
/// </summary>
private string inputFilePath=null;
/// <summary>
/// 输出文件路径
/// </summary>
private string outFilePath=null;
/// <summary>
/// 加密密钥
/// </summary>
private string encryptKey=null;
/// <summary>
/// 解密密钥
/// </summary>
private string decryptKey=null;
/// <summary>
/// 提示信息
/// </summary>
private string noteMessage=null;
#endregion
#region 公共属性
/// <summary>
/// 输入字符串
/// </summary>
public string InputString
{
get{return inputString;}
set{inputString=value;}
}
/// <summary>
/// 输出字符串
/// </summary>
public string OutString
{
get{return outString;}
set{outString=value;}
}
/// <summary>
/// 输入文件路径
/// </summary>
public string InputFilePath
{
get{return inputFilePath;}
set{inputFilePath=value;}
}
/// <summary>
/// 输出文件路径
/// </summary>
public string OutFilePath
{
get{return outFilePath;}
set{outFilePath=value;}
}
/// <summary>
/// 加密密钥
/// </summary>
public string EncryptKey
{
get{return encryptKey;}
set{encryptKey=value;}
}
/// <summary>
/// 解密密钥
/// </summary>
public string DecryptKey
{
get{return decryptKey;}
set{decryptKey=value;}
}
/// <summary>
/// 错误信息
/// </summary>
public string NoteMessage
{
get{return noteMessage;}
set{noteMessage=value;}
}
#endregion
#region 构造函数
public DESEncryptor()
{
//
// TODO: 在此处添加构造函数逻辑
//
}
#endregion
#region DES加密字符串
/// <summary>
/// 加密字符串
/// 注意:密钥必须为８位
/// </summary>
/// <param name="strText">字符串</param>
/// <param name="encryptKey">密钥</param>
public void DesEncrypt()
{
byte[] byKey=null;
byte[] IV= {0x12, 0x34, 0x56, 0x78, 0x90, 0xAB, 0xCD, 0xEF};
try
{
byKey = System.Text.Encoding.UTF8.GetBytes(this.encryptKey.Substring(0,8));
DESCryptoServiceProvider des = new DESCryptoServiceProvider();
byte[] inputByteArray = Encoding.UTF8.GetBytes(this.inputString);
MemoryStream ms = new MemoryStream();
CryptoStream cs = new CryptoStream(ms, des.CreateEncryptor(byKey, IV), CryptoStreamMode.Write) ;
cs.Write(inputByteArray, 0, inputByteArray.Length);
cs.FlushFinalBlock();
this.outString=Convert.ToBase64String(ms.ToArray());
}
catch(System.Exception error)
{
this.noteMessage=error.Message;
}
}
#endregion
#region DES解密字符串
/// <summary>
/// 解密字符串
/// </summary>
/// <param name="this.inputString">加了密的字符串</param>
/// <param name="decryptKey">密钥</param>
public void DesDecrypt()
{
byte[] byKey = null;
byte[] IV= {0x12, 0x34, 0x56, 0x78, 0x90, 0xAB, 0xCD, 0xEF};
byte[] inputByteArray = new Byte[this.inputString.Length];
try
{
byKey = System.Text.Encoding.UTF8.GetBytes(decryptKey.Substring(0,8));
DESCryptoServiceProvider des = new DESCryptoServiceProvider();
inputByteArray = Convert.FromBase64String(this.inputString);
MemoryStream ms = new MemoryStream();
CryptoStream cs = new CryptoStream(ms, des.CreateDecryptor(byKey, IV), CryptoStreamMode.Write);
cs.Write(inputByteArray, 0, inputByteArray.Length);
cs.FlushFinalBlock();
System.Text.Encoding encoding = new System.Text.UTF8Encoding();
this.outString=encoding.GetString(ms.ToArray());
}
catch(System.Exception error)
{
this.noteMessage=error.Message;
}
}
#endregion
#region DES加密文件
/// <summary>
/// DES加密文件
/// </summary>
/// <param name="this.inputFilePath">源文件路径</param>
/// <param name="this.outFilePath">输出文件路径</param>
/// <param name="encryptKey">密钥</param>
public void FileDesEncrypt()
{
byte[] byKey=null;
byte[] IV= {0x12, 0x34, 0x56, 0x78, 0x90, 0xAB, 0xCD, 0xEF};
try
{
byKey = System.Text.Encoding.UTF8.GetBytes(this.encryptKey.Substring(0,8));
FileStream fin = new FileStream(this.inputFilePath, FileMode.Open, FileAccess.Read);
FileStream fout = new FileStream(this.outFilePath, FileMode.OpenOrCreate, FileAccess.Write);
fout.SetLength(0);
//Create variables to help with read and write.
byte[] bin = new byte[100]; //This is intermediate storage for the encryption.
long rdlen = 0; //This is the total number of bytes written.
long totlen = fin.Length; //This is the total length of the input file.
int len; //This is the number of bytes to be written at a time.
DES des = new DESCryptoServiceProvider();
CryptoStream encStream = new CryptoStream(fout, des.CreateEncryptor(byKey, IV), CryptoStreamMode.Write);


//Read from the input file, then encrypt and write to the output file.
while(rdlen < totlen)
{
len = fin.Read(bin, 0, 100);
encStream.Write(bin, 0, len);
rdlen = rdlen + len;
}

encStream.Close();
fout.Close();
fin.Close();


}
catch(System.Exception error)
{
this.noteMessage=error.Message.ToString();

}
}
#endregion
#region DES解密文件
/// <summary>
/// 解密文件
/// </summary>
/// <param name="this.inputFilePath">加密了的文件路径</param>
/// <param name="this.outFilePath">输出文件路径</param>
/// <param name="decryptKey">密钥</param>
public void FileDesDecrypt()
{
byte[] byKey = null;
byte[] IV= {0x12, 0x34, 0x56, 0x78, 0x90, 0xAB, 0xCD, 0xEF};
try
{
byKey = System.Text.Encoding.UTF8.GetBytes(decryptKey.Substring(0,8));
FileStream fin = new FileStream(this.inputFilePath, FileMode.Open, FileAccess.Read);
FileStream fout = new FileStream(this.outFilePath, FileMode.OpenOrCreate, FileAccess.Write);
fout.SetLength(0);
//Create variables to help with read and write.
byte[] bin = new byte[100]; //This is intermediate storage for the encryption.
long rdlen = 0; //This is the total number of bytes written.
long totlen = fin.Length; //This is the total length of the input file.
int len; //This is the number of bytes to be written at a time.
DES des = new DESCryptoServiceProvider();
CryptoStream encStream = new CryptoStream(fout, des.CreateDecryptor(byKey, IV), CryptoStreamMode.Write);


//Read from the input file, then encrypt and write to the output file.
while(rdlen < totlen)
{
len = fin.Read(bin, 0, 100);
encStream.Write(bin, 0, len);
rdlen = rdlen + len;
}

encStream.Close();
fout.Close();
fin.Close();
}
catch(System.Exception error)
{
this.noteMessage=error.Message.ToString();
}
}
#endregion
#region MD5
/// <summary>
/// MD5 Encrypt
/// </summary>
/// <param name="strText">text</param>
/// <returns>md5 Encrypt string</returns>
public void MD5Encrypt()
{
MD5 md5 = new MD5CryptoServiceProvider();
byte[] result = md5.ComputeHash(System.Text.Encoding.Default.GetBytes(this.inputString));
this.outString=System.Text.Encoding.Default.GetString(result);
}
#endregion

}
}