對文件進行DES加密與解密

/// <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);
        }
    }
}