LoomRandom.php

   1 <?php
   2
   3   // Cryptographically secure random number generation
   4
   5 class LoomRandom {
   6
   7   var $urandom_filehandle;      // /dev/urandom file handle
   8   var $use_urandom;             // false if we can't open /dev/urandom
   9
  10   function LoomRandom() {
  11     $this->urandom_filehandle = false;
  12     $this->use_urandom = true;
  13   }
  14
  15   // Return $num random bytes from /dev/urandom
  16   function urandom_bytes($num) {
  17     if ($num < 0)
  18       err("NUM must be nonnegative in urandom_bytes");
  19     if ($this->use_urandom && !$this->urandom_filehandle) {
  20       $file = @fopen("/dev/urandom", "r");
  21       if (!$file) $this->use_urandom = false;
  22       else $this->urandom_filehandle = $file;
  23     }
  24     $res = '';
  25     if ($this->use_urandom) {
  26       while (strlen($res) < $num) {
  27         $res .= fread($this->urandom_filehandle, $num - strlen($res));
  28       }
  29     } else {
  30       for ($i=0; $i<$num; $i++) {
  31         $res .= chr(mt_rand(0, 255));
  32       }
  33     }
  34     return $res;
  35   }
  36
  37   // Return a random 128-bit location, as hex
  38   function random_id() {
  39     $res = bin2hex($this->urandom_bytes(16));
  40     if (strlen($res) < 32) $res = str_repeat("0", 32 - strlen($res)) . $res;
  41     return $res;
  42   }
  43
  44 }
  45
  46 /* testing code
  47
  48 $random = new LoomRandom();
  49 echo $random->random_id() . "\n";
  50
  51 */
  52
  53 // Copyright 2008 Bill St. Clair
  54 //
  55 // Licensed under the Apache License, Version 2.0 (the "License");
  56 // you may not use this file except in compliance with the License.
  57 // You may obtain a copy of the License at
  58 //
  59 //     http://www.apache.org/licenses/LICENSE-2.0
  60 //
  61 // Unless required by applicable law or agreed to in writing, software
  62 // distributed under the License is distributed on an "AS IS" BASIS,
  63 // WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
  64 // See the License for the specific language governing permissions
  65 // and limitations under the License.
  66
  67 ?>