password generator code

**jscheuer1** · 01-07-2007, 08:34 AM

Due to concerns about demands upon the server, javascript is often preferred as the first method (when available) to be used, with server side code waiting in the wings as a backup should the user not have javascript enabled. Once javascript has delivered the data to a form element, the server should be able to pick it up from there and stick it in the database. With that in mind and my seeing that the code originally presented here looked way too involved, I've come up with a shorter javascript method for generating passwords:

Code:

<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN" "http://www.w3.org/TR/1999/REC-html401-19991224/loose.dtd">
<html>
<head>
<title>Password Gen - Demo</title>
<meta http-equiv="Content-Type" content="text/html; charset=iso-8859-1">
<script type="text/javascript">
function random_pass(len){
var tokens=[];
for (var j = 0; j < len; j++){
tokens[tokens.length]=String.fromCharCode(parseInt((Math.floor(Math.random()*26)+65).toString(16),16));
tokens[tokens.length]=String.fromCharCode(parseInt((Math.floor(Math.random()*26)+97).toString(16),16));
tokens[tokens.length]=Math.floor(Math.random()*10)
}
tokens.sort(function() {return 0.5 - Math.random();}) //thanks to Mike (aka Mwinter) :)
tokens.length=len;
return tokens.join('');
}
</script>
</head>
<body>
<input type="text" size="9" id="pass" readonly style="font-family:serif;font-size:120%;"> 
<input type="button" value="Gen" onclick="document.getElementById('pass').value=random_pass(7);"> 
<input type="button" value="select" onclick="document.getElementById('pass').select();">
</body>
</html>

Notes: Generates passwords consisting only of letters (upper and lower case) and numbers.

Usage of the function is:

random_pass(length)

where length is the desired number of characters in the password. The code could probably be simplified further but, you will note that it generates on the order of three times as many characters as will be required and then randomizes those before choosing the finished password. I think this makes for a robustly random password. What could probably be simplified most is the generation of the upper and lower case letters, I'm just not sure how.

**exed** · 01-07-2007, 01:10 PM

Originally Posted by djr33

Also, using the ascii codes really makes sense in this case, since it can be changed fairly easily. But doing it like that could work as well.

Do you have a test page?

I update script, it's working correctly.

test page:
http://ligr.info/_tools/passgen.php?passlen=400

passlen=xxx - option for length test

jscheuer1, very, very good script.
I could not find this function String.fromCharCode.
Thank you!

**Twey** · 01-07-2007, 01:44 PM

Javascript:

Code:

function PasswordGenerator(defaultLength) {
  var i;

  this.length = defaultLength || 8;
  this.data = [];
  this.weighted = [];

  for(i = 0x20; i < 0x7F; ++i)
    this.data.push(
      {
        'weight' : 1,
        'datum' : String.fromCharCode(i)
      }
    );

  this.recalcWeights();
}

PasswordGenerator.prototype.setLength = function(length) {
  var l;
  if(!isNaN(l = parseInt(length)))
    return (this.length = length);
  else return this.length;
};

PasswordGenerator.prototype.clearData = function() {
  this.data = [];
  this.recalcWeights();
};

PasswordGenerator.prototype.findDatum = function(datum) {
  for(var i = 0; i < this.data.length; ++i)
    if(this.data[i].datum === datum)
      return i;
  return -1;
};

PasswordGenerator.prototype.addData = function(data, weight) {
  var weight = parseInt(weight, 10);
  if(isNaN(weight))
    weight = 1;
  for(var i = 0, c; !isNaN((c = data.charAt(i)).charCodeAt(0)); ++i)
    this.addDatum(c, weight);
};

PasswordGenerator.prototype.addDatum = function(datum, weight) {
  var weight = parseInt(weight, 10);
  if(isNaN(weight))
    weight = 1;

  if(this.findDatum(datum) !== -1)
    this.removeDatum(datum);
  
  this.data.push({'datum' : datum, 'weight' : weight});
  this.recalcWeights();
};

PasswordGenerator.prototype.removeDatum = function(datum) {
  var index = this.findDatum(datum);
  if(index === -1)
    return null;
  this.data.splice(index, 1);
  this.recalcWeights();
};

PasswordGenerator.prototype.recalcWeights = function() {
  for(var i = 0; i < this.data.length; ++i)
    for(var j = 0; j < this.data[i].weight; ++j)
      this.weighted.push(this.data[i].datum);
};

PasswordGenerator.prototype.getCharacter = function() {
  return this.weighted[Math.floor(Math.random() * this.weighted.length)];
};

PasswordGenerator.prototype.generate = function() {
  var ret = "";
  for(var i = 0; i < this.length; ++i)
    ret += this.getCharacter();
  return ret;
};

Or PHP:

Code:

class PasswordGenerator {
  var $length;
  var $data;
  var $weighted;

  function PasswordGenerator($defaultLength = 8) {
    $this->length = $defaultLength;
    $this->data = array();
    $this->weighted = array();

    for($i = 0x20; $i < 0x7F; ++$i)
      array_push($this->data, array('weight' => 1, 'datum' => chr($i)));

    $this->recalcWeights();
  }

  function setLength($length = 0) {
    if($length < 1) return $this->length;
    return $this->length;
  }

  function clearData() {
    $this->data = array();
    $this->recalcWeights();
  }

  function findDatum($datum) {
    foreach($this->data as $key => $val)
      if($val === $datum)
        return $key;
    return -1;
  }

  function addData($data, $weight = 1) {
    $c;
    for($i = 0; (ord($c = $data[$i])); ++$i)
      $this->addDatum($c, $weight);
  }

  function addDatum($datum, $weight = 1) {
    if($this->findDatum($datum) !== -1)
      $this->removeDatum($datum);
    array_push($this->data, array('datum' => $datum, 'weight' => $weight));
    $this->recalcWeights();
  }

  function removeDatum($datum) {
    $index = $this->findDatum($datum);
    if($index === -1)
      return null;
    array_splice($this->data, $index, 1);
    $this->recalcWeights();
  }

  function recalcWeights() {
    foreach($this->data as $key => $val)
      for($j = 0; $j < $val['weight']; ++$j)
        array_push($this->weighted, $val['datum']);
  }

  function getCharacter() {
    return $this->weighted[rand(0, count($this->weighted) - 1)];
  }

  function generate() {
    $ret = "";
    for($i = 0; $i < $this->length; ++$i)
      $ret .= $this->getCharacter();
    return $ret;
  }
}

Tested slightly but not extensively.

**jscheuer1** · 01-08-2007, 08:53 AM

Thanks, Twey. I knew that finding the alphabet characters could be simplified. The function is now very short and sweet and defaults to a 7 character password (usage is the same as before):

Code:

function random_pass(l){
var t='', l=l||7, c=function(hx){return String.fromCharCode(Math.floor(Math.random()*0x1a)+hx);};
for (var j=0, g=Math.floor(Math.random()*3); j<l; j++, g=Math.floor(Math.random()*3))
t+=g>1? c(0x41) : g? c(0x61) : Math.floor(Math.random()*10);
return t;
}

The page is a little more complex owing to style used to make the output clearer:

Code:

<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN" "http://www.w3.org/TR/1999/REC-html401-19991224/loose.dtd">
<html>
<head>
<title>Password Gen - Demo</title>
<meta http-equiv="Content-Type" content="text/html; charset=iso-8859-1">
<style type="text/css">
#pass {
font-family:serif;
font-size:120%;
letter-spacing:2px;
}
</style>
<script type="text/javascript">
function random_pass(l){
var t='', l=l||7, c=function(hx){return String.fromCharCode(Math.floor(Math.random()*0x1a)+hx);};
for (var j=0, g=Math.floor(Math.random()*3); j<l; j++, g=Math.floor(Math.random()*3))
t+=g>1? c(0x41) : g? c(0x61) : Math.floor(Math.random()*10);
return t;
}
</script>
</head>
<body>
<input id="pass" type="text" readonly size="9"> 
<input type="button" value="Gen" onclick="document.getElementById('pass').value=random_pass();"> 
<input type="button" value="select" onclick="document.getElementById('pass').select();">
</body>
</html>

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