note 105587 added to function.mt-rand

This function has limited entrophy. So, if you want to create random string, it will produce only about 2 billion different strings, no matter the length of the string. This can be serous security issue if you are using such strings for session indentifiers, passwords etc. Many times I have wanted to create *propper* base-64 string (containing only printable characters) of arbitrary length for many purposes. I wrote a function that checks if UNIX random generator is available and uses in that case. If not, it tries to increase the entrophy by accounting in the script execution time. Here is the function, just try it out! function random($len) { if (@is_readable('/dev/urandom')) { $f=fopen('/dev/urandom', 'r'); $urandom=fread($f, $len); fclose($f); } $return=''; for ($i=0;$i<$len;++$i) { if (!isset($urandom)) { if ($i%2==0) mt_srand(time()%2147 * 1000000 + (double)microtime() * 1000000); $rand=48+mt_rand()%64; } else $rand=48+ord($urandom[$i])%64; if ($rand>57) $rand+=7; if ($rand>90) $rand+=6; if ($rand==123) $rand=45; if ($rand==124) $rand=46; $return.=chr($rand); } return $return; } ---- Server IP: 91.185.195.14 Probable Submitter: 95.176.219.82 ---- Manual Page -- http://www.php.net/manual/en/function.mt-rand.php Edit -- https://master.php.net/note/edit/105587 Del: integrated -- https://master.php.net/note/delete/105587/integrated Del: useless -- https://master.php.net/note/delete/105587/useless Del: bad code -- https://master.php.net/note/delete/105587/bad+code Del: spam -- https://master.php.net/note/delete/105587/spam Del: non-english -- https://master.php.net/note/delete/105587/non-english Del: in docs -- https://master.php.net/note/delete/105587/in+docs Del: other reasons-- https://master.php.net/note/delete/105587 Reject -- https://master.php.net/note/reject/105587 Search -- https://master.php.net/manage/user-notes.php