Division by zero!

schwim2

Well, it looks like I've finally managed to end the world. I'm trying to use an encryption function that I have had lying around when attempting to use it, I get the following error:

Warning: in file file.php on line 1457: Division by zero

The function:

$enckey = 'NotTheRealEncKey';
function encrypt($string, $enckey) {
  $result = '';
  for($i=0; $i<strlen($string); $i++) {
    $char = substr($string, $i, 1);
    $keychar = substr($enckey, ($i % strlen($enckey))-1, 1);
    $char = chr(ord($char)+ord($keychar));
    $result.=$char;
  }

  return base64_encode($result);
}

The line in question is:

$keychar = substr($enckey, ($i % strlen($enckey))-1, 1);

and the string getting encrypted(it's a randomly generated token:

19323424651482417148

I've been googling but I'm coming up empty. Could someone perhaps set me on the path to righteousness by telling me what I'm doing wrong?

Thanks for your time!

NogDog

Is this line 1457?

    $keychar = substr($enckey, ($i % strlen($enckey))-1, 1);

If so, then probably $enckey is a zero-length key for some reason.

Side note: don't do your own encryption, as it's almost certain to be less secure than any of the current, standard libraries/functions.

schwim2

Hi there, Nog and thanks for the help!

You were of course correct. I has missepelled enckey.

Can I ask what library you would suggest for something like this of limited characters? It doesn't have to be a set number of characters, it will be used in a URL and it needs to be as random as possible.

Thanks for your time!

NogDog

Question: do you actually unencrypt it, or is it really just an issue of wanting to create a hash of something that will then be shared/stored somewhere (similar to password hashing)? The "limited characters" aspect suggests to me you're just creating a hash.

schwim2

It is indeed an issue of just wanting to create a hash. Sorry for not specifying.

NogDog

In that case, I'd just use the hash() function.

$hashedThingy = hash('sha256', $thingy);

Derokorian

If you're just looking for a random string, since you mention the string is a randomly generated number, you might want to look at [man]random_bytes[/man] if you're on PHP7+