how to secure file upload ?

[plodos]

i have a upload/ directory...there are some pics. inside of the that directory

when I upload the files, link looks like

www.aaaa.com/upload/a.gif

www.aaaa.com/upload/sdf.gif

www.aaaa.com/upload/sadasd.gif

these are not secure...somebody can download all the pictures by the help of flashget or other programs...

 

I want to add HASH code before the upload like..HASH is good? there will be lots of different directories:S

 

www.aaaa.com/upload/1f3870be274f6c49b3e31a0c6728957f/a.gif

www.aaaa.com/upload/1f3870be274f6c49b3e31aasdasdadd/sdf.gif

www.aaaa.com/upload/1f3870be274f6c49b3e31a0casdasddk/sadasd.gif

now thats not easy to find the pictures ( in my opinion )

 

I dont know how will I add this hash code inside of the these script :s

Who can help me!!!

 

And other question....is it good solution method ? or Could you tell me whats better to keep these pictures from unwanted users( easy way is better for me to understand and apply )...

 

thnx for helping me !!!

 

<?php
if ((($_FILES["file"]["type"] == "image/gif")
|| ($_FILES["file"]["type"] == "image/jpeg")
|| ($_FILES["file"]["type"] == "image/pjpeg"))
&& ($_FILES["file"]["size"] < 20000))
  {
  if ($_FILES["file"]["error"] > 0)
    {
    echo "Return Code: " . $_FILES["file"]["error"] . "<br />";
    }
  else
    {
    echo "Upload: " . $_FILES["file"]["name"] . "<br />";
    echo "Type: " . $_FILES["file"]["type"] . "<br />";
    echo "Size: " . ($_FILES["file"]["size"] / 1024) . " Kb<br />";
    echo "Temp file: " . $_FILES["file"]["tmp_name"] . "<br />";

    if (file_exists("upload/" . $_FILES["file"]["name"]))
      {
      echo $_FILES["file"]["name"] . " already exists. ";
      }
    else
      {
      move_uploaded_file($_FILES["file"]["tmp_name"],
      "upload/" . $_FILES["file"]["name"]);
      echo "Stored in: " . "upload/" . $_FILES["file"]["name"];
      }
    }
  }
else
  {
  echo "Invalid file";
  }
?>

[MadTechie]

or you could turn off directory listing via .htaccess.. the fact remains if anyone can access the image then anyone can steal the image.. removing the listing makes it a little harder