encrypting and decrypting file in c#

it's work only for text file can any help me how to do it for all kind of files ex: pdf, word etc
the below code encoding all files but while in decrypting it's decoded to some char

plz help me............

protected void FileUpload(int size,string CntType)
{ 
   conn.Open();
   SqlCommand cmd = new SqlCommand("insert into FileDetails values('" + File1.FileName + "','" + CntType + "','" + size + "','" + DateTime.Now + "')", conn);
   cmd.ExecuteNonQuery();
   cmd = new SqlCommand("select max(FileID) from FileDetails", conn);
   using (SqlDataReader dr = cmd.ExecuteReader())
   if (dr.Read())    
   {
      lstFile.Items.Clear();
      lstFile.Items.Add(" \t Keyword Encryption ---->  ");
      lstFile.Items.Add("----------------------------------------------------");
      string[] str=txtKeyword.Text.Split(',');
      foreach(string word in str)
      {
         string strEncrypt = Homomorphic.DesEncrypt(word.ToLower(), true);
         lstFile.Items.Add(" \t   " + strEncrypt);
         SqlCommand cmdindex = new SqlCommand("insert into Indexing values(" + dr.GetValue(0) + ",'"  + strEncrypt + "')", conn);
         cmdindex.ExecuteNonQuery();
      }
      dr.Close();
      lstFile.Items.Add("------------------------------------------------------------");
   }
}

protected void btnUpload_Click(object sender, System.EventArgs e)
{
   try
      {
	for(int i=0;i<request.files.count;i++)>
	{
	    if(Request.Files[i].FileName.Trim().Length >0) 
	    {
		HttpPostedFile file=Request.Files[i];
   	        if(file!=null && file.FileName.Length>0)
                {
                   string strmsg = string.Empty;
                   byte[] fileData = new byte[file.ContentLength];
                   file.InputStream.Read(fileData, 0, file.ContentLength);
                   strmsg = System.Text.Encoding.UTF8.GetString(fileData); 
                   string ps = Homomorphic.DesEncrypt(strmsg.ToLower(),true); 
                   using (StreamWriter writer = new StreamWriter(Path.Combine(GetCurDir(),                Path.GetFileName(file.FileName)), true))
                    {
                           writer.WriteLine(ps);
                           writer.Flush();
                    }
                    FileUpload(file.ContentLength,file.ContentType);
                    Response.Write("<script language='javascript'>alert('Encrypted & Uploaded !')</script>");
                    lstFile.Items.Add(" \t File Encryption  ----> ");
                    lstFile.Items.Add("------------------------------------------------------");
                    lstFile.Items.Add(" \t  " + ps);
                }
            }
         }
        BindData();
      }
      catch(Exception ex)
       {
            lblError.Text=ex.Message;
       }
}

Tags: C#, ASP.NET, Encryption