加密，解密

using System;
using System.Security.Cryptography;
using System.IO;
using System.Text;
using System.Globalization;

/// <summary>
/// 对指定内容进行DES加密和解密处理
/// </summary>
public sealed class DESEncrypt
{
/// <summary>
/// 对字符串进行DES加密
/// </summary>
/// <param name="sourcestring">待加密的字符串</param>
/// <param name="key">必须长度等于8的字符串</param>
/// <param name="iv">必须长度大于等于8的字符串</param>
/// <returns>加密后的BASE64编码的字符串</returns>
internal static string Encrypt(string src, string key, string iv)
{
byte[] byteKey = Encoding.Default.GetBytes(key);
byte[] byteIv = Encoding.Default.GetBytes(iv);
DESCryptoServiceProvider des = new DESCryptoServiceProvider();
using (MemoryStream ms = new MemoryStream())
{

try
{
byte[] data = Encoding.Default.GetBytes(src);
using (CryptoStream cs = new CryptoStream(ms, des.CreateEncryptor(byteKey, byteIv), CryptoStreamMode.Write))
{
cs.Write(data, 0, data.Length);
cs.FlushFinalBlock();
}
return Convert.ToBase64String(ms.ToArray());
}
catch
{
throw;
}
}
}

/// <summary>
/// 对DES加密后的字符串进行解密
/// </summary>
/// <param name="encryptedString">待解密的字符串</param>
/// <param name="key">同加密时所采用的key</param>
/// <param name="iv">同加密时所采用的iv</param>
/// <returns>解密后的字符串</returns>
internal static string Decrypt(string src, string key, string iv)
{
byte[] byteKey = Encoding.Default.GetBytes(key);
byte[] byteIv = Encoding.Default.GetBytes(iv);
DESCryptoServiceProvider des = new DESCryptoServiceProvider();

using (MemoryStream ms = new MemoryStream())
{
try
{
byte[] data = Convert.FromBase64String(src);
using (CryptoStream cs = new CryptoStream(ms, des.CreateDecryptor(byteKey, byteIv), CryptoStreamMode.Write))
{
cs.Write(data, 0, data.Length);
cs.FlushFinalBlock();
}
return Encoding.Default.GetString(ms.ToArray());
}
catch
{
throw;
}
}
}

/// <summary>
/// 对文件内容进行DES加密
/// </summary>
/// <param name="sourceFile">待加密的文件绝对路径</param>
/// <param name="destFile">加密后的文件保存的绝对路径</param>
/// <param name="key">必须长度等于8的字符串</param>
/// <param name="iv">必须长度大于等于8的字符串</param>
internal static void EncryptFile(string sourceFile, string destFile, string key, string iv)
{
if (!File.Exists(sourceFile))
throw new FileNotFoundException("指定的文件路径不存在！", sourceFile);

byte[] byteKey = Encoding.Default.GetBytes(key);
byte[] byteIV = Encoding.Default.GetBytes(iv);
DESCryptoServiceProvider des = new DESCryptoServiceProvider();
byte[] byteFile = File.ReadAllBytes(sourceFile);

using (FileStream fs = new FileStream(destFile, FileMode.Create, FileAccess.Write))
{
try
{
using (CryptoStream cs = new CryptoStream(fs, des.CreateEncryptor(byteKey, byteIV), CryptoStreamMode.Write))
{
cs.Write(byteFile, 0, byteFile.Length);
cs.FlushFinalBlock();
}
}
catch
{
throw;
}

finally
{
fs.Close();
}
}
}

/// <summary>
/// Encrypts the file.
/// 对文件内容进行DES加密，加密后覆盖掉原来的文件
/// </summary>
/// <param name="sourceFile">The source file.待加密的文件的绝对路径</param>
/// <param name="key">必须长度等于8的字符串</param>
/// <param name="iv">必须长度大于等于8的字符串</param>
internal static void EncryptFile(string sourceFile, string key, string iv)
{
EncryptFile(sourceFile, sourceFile, key, iv);
}

/// <summary>
/// 对文件内容进行DES解密
/// </summary>
/// <param name="sourceFile">待解密的文件绝对路径</param>
/// <param name="destFile">解密后的文件保存的绝对路径</param>
/// <param name="key">同加密时所采用的key</param>
/// <param name="iv">同加密时所采用的iv</param>
internal static void DecryptFile(string sourceFile, string destFile, string key, string iv)
{
if (!File.Exists(sourceFile)) throw new FileNotFoundException("指定的文件路径不存在！", sourceFile);
byte[] byteKey = Encoding.Default.GetBytes(key);
byte[] byteIV = Encoding.Default.GetBytes(iv);
DESCryptoServiceProvider des = new DESCryptoServiceProvider();
byte[] byteFile = File.ReadAllBytes(sourceFile);

using (FileStream fs = new FileStream(destFile, FileMode.Create, FileAccess.Write))
{
try
{
using (CryptoStream cs = new CryptoStream(fs, des.CreateDecryptor(byteKey, byteIV), CryptoStreamMode.Write))
{
cs.Write(byteFile, 0, byteFile.Length);
cs.FlushFinalBlock();
}
}
catch
{
throw;
}
finally
{
fs.Close();
}
}
}

/// <summary>
/// 对文件内容进行DES解密，加密后覆盖掉原来的文件
/// </summary>
/// <param name="sourceFile">待解密的文件的绝对路径</param>
/// <param name="key">同加密时所采用的key</param>
/// <param name="iv">同加密时所采用的iv</param>
internal static void DecryptFile(string sourceFile, string key, string iv)
{
DecryptFile(sourceFile, sourceFile, key, iv);
}
}