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