C# DES 加密/解密，支持文件和中文/UNICODE字符，返回BASE64編碼字符串

using System;
using System.Collections.Generic;
using System.Text;
using System.IO;
using System.Security;
using System.Security.Cryptography;
/*----------------------------------------------
 *  DES加密、解密類庫，字符串加密結果使用BASE64編碼返回，支持文件的加密和解密
 *  作者： 三角貓/DeltaCat
 *  網址： http://www.zu14.cn
 *  轉載務必保留此信息
 * ---------------------------------------------
 */
namespace ZU14
{
    public sealed class DES
    {
        string iv = "1234的yzo";
        string key = "123在yzo";
        /// <summary>
        /// DES加密偏移量，必須是>=8位長的字符串
        /// </summary>
        public string IV
        {
            get { return iv; }
            set { iv = value; }
        }
        /// <summary>
        /// DES加密的私鑰，必須是8位長的字符串
        /// </summary>
        public string Key
        {
            get { return key; }
            set { key = value; }
        }
        /// <summary>
        /// 對字符串進行DES加密
        /// </summary>
        /// <param name="sourceString">待加密的字符串</param>
        /// <returns>加密後的BASE64編碼的字符串</returns>
        public string Encrypt(string sourceString)
        {
            byte[] btKey = Encoding.Default.GetBytes(key);
            byte[] btIV = Encoding.Default.GetBytes(iv);
            DESCryptoServiceProvider des = new DESCryptoServiceProvider();
            using (MemoryStream ms = new MemoryStream())
            {
                byte[] inData = Encoding.Default.GetBytes(sourceString);
                try
                {
                    using (CryptoStream cs = new CryptoStream(ms, des.CreateEncryptor(btKey, btIV), CryptoStreamMode.Write))
                    {
                        cs.Write(inData, 0, inData.Length);
                        cs.FlushFinalBlock();
                    }
                    return Convert.ToBase64String(ms.ToArray());
                }
                catch
                {
                    throw;
                }
            }
        }
        /// <summary>
        /// 對DES加密後的字符串進行解密
        /// </summary>
        /// <param name="encryptedString">待解密的字符串</param>
        /// <returns>解密後的字符串</returns>
        public string Decrypt(string encryptedString)
        {
            byte[] btKey = Encoding.Default.GetBytes(key);
            byte[] btIV = Encoding.Default.GetBytes(iv);
            DESCryptoServiceProvider des = new DESCryptoServiceProvider();
            using (MemoryStream ms = new MemoryStream())
            {
                byte[] inData = Convert.FromBase64String(encryptedString);
                try
                {
                    using (CryptoStream cs = new CryptoStream(ms, des.CreateDecryptor(btKey, btIV), CryptoStreamMode.Write))
                    {
                        cs.Write(inData, 0, inData.Length);
                        cs.FlushFinalBlock();
                    }
                    return Encoding.Default.GetString(ms.ToArray());
                }
                catch
                {
                    throw;
                }
            }
        }
        /// <summary>
        /// 對文件內容進行DES加密
        /// </summary>
        /// <param name="sourceFile">待加密的文件絕對路徑</param>
        /// <param name="destFile">加密後的文件保存的絕對路徑</param>
        public void EncryptFile(string sourceFile, string destFile)
        {
            if (!File.Exists(sourceFile)) throw new FileNotFoundException("指定的文件路徑不存在！", sourceFile);
            byte[] btKey = Encoding.Default.GetBytes(key);
            byte[] btIV = Encoding.Default.GetBytes(iv);
            DESCryptoServiceProvider des = new DESCryptoServiceProvider();
            byte[] btFile = File.ReadAllBytes(sourceFile);
            using (FileStream fs = new FileStream(destFile, FileMode.Create, FileAccess.Write))
            {
                try
                {
                    using (CryptoStream cs = new CryptoStream(fs, des.CreateEncryptor(btKey, btIV), CryptoStreamMode.Write))
                    {
                        cs.Write(btFile, 0, btFile.Length);
                        cs.FlushFinalBlock();
                    }
                }
                catch
                {
                    throw;
                }
                finally
                {
                    fs.Close();
                }
            }
        }
        /// <summary>
        /// 對文件內容進行DES加密，加密後覆蓋掉原來的文件
        /// </summary>
        /// <param name="sourceFile">待加密的文件的絕對路徑</param>
        public void EncryptFile(string sourceFile)
        {
            EncryptFile(sourceFile, sourceFile);
        }
        /// <summary>
        /// 對文件內容進行DES解密
        /// </summary>
        /// <param name="sourceFile">待解密的文件絕對路徑</param>
        /// <param name="destFile">解密後的文件保存的絕對路徑</param>
        public void DecryptFile(string sourceFile, string destFile)
        {
            if (!File.Exists(sourceFile)) throw new FileNotFoundException("指定的文件路徑不存在！", sourceFile);
            byte[] btKey = Encoding.Default.GetBytes(key);
            byte[] btIV = Encoding.Default.GetBytes(iv);
            DESCryptoServiceProvider des = new DESCryptoServiceProvider();
            byte[] btFile = File.ReadAllBytes(sourceFile);
            using (FileStream fs = new FileStream(destFile, FileMode.Create, FileAccess.Write))
            {
                try
                {
                    using (CryptoStream cs = new CryptoStream(fs, des.CreateDecryptor(btKey, btIV), CryptoStreamMode.Write))
                    {
                        cs.Write(btFile, 0, btFile.Length);
                        cs.FlushFinalBlock();
                    }
                }
                catch
                {
                    throw;
                }
                finally
                {
                    fs.Close();
                }
            }
        }
        /// <summary>
        /// 對文件內容進行DES解密，加密後覆蓋掉原來的文件
        /// </summary>
        /// <param name="sourceFile">待解密的文件的絕對路徑</param>
        public void DecryptFile(string sourceFile)
        {
            DecryptFile(sourceFile, sourceFile);
        }
    }
}

使用實例：

ZU14.DES des = new ZU14.DES();
des.IV = "abcd哈哈笑";
des.Key = "必須八位";
string es = des.Encrypt("在");
Console.WriteLine(es);
Console.Write(des.Decrypt(es));
des.EncryptFile(@"d:\a.txt", @"d:\b.txt");
des.DecryptFile(@"d:\b.txt");
Console.ReadKey(true);