Generate random bytes.
{
$length = (int) $length;
$sslStr = '';
if (function_exists('openssl_random_pseudo_bytes')
&& (version_compare(PHP_VERSION, '5.3.4') >= 0 || IS_WIN))
{
$sslStr = openssl_random_pseudo_bytes($length, $strong);
if ($strong)
{
return $sslStr;
}
}
$bitsPerRound = 2;
$maxTimeMicro = 400;
$shaHashLength = 20;
$randomStr = '';
$total = $length;
$urandom = false;
$handle = null;
if (function_exists('stream_set_read_buffer') && @is_readable('/dev/urandom'))
{
$handle = @fopen('/dev/urandom', 'rb');
if ($handle)
{
$urandom = true;
}
}
while ($length > strlen($randomStr))
{
$bytes = ($total > $shaHashLength)? $shaHashLength : $total;
$total -= $bytes;
$entropy = rand() . uniqid(mt_rand(), true) . $sslStr;
$entropy .= implode('', @fstat(fopen(__FILE__, 'r')));
$entropy .= memory_get_usage();
$sslStr = '';
if ($urandom)
{
stream_set_read_buffer($handle, 0);
$entropy .= @fread($handle, $bytes);
}
else
{
$samples = 3;
$duration = 0;
for ($pass = 0; $pass < $samples; ++$pass)
{
$microStart = microtime(true) * 1000000;
$hash = sha1(mt_rand(), true);
for ($count = 0; $count < 50; ++$count)
{
$hash = sha1($hash, true);
}
$microEnd = microtime(true) * 1000000;
$entropy .= $microStart . $microEnd;
if ($microStart >= $microEnd)
{
$microEnd += 1000000;
}
$duration += $microEnd - $microStart;
}
$duration = $duration / $samples;
$rounds = (int) (($maxTimeMicro / $duration) * 50);
$iter = $bytes * (int) ceil(8 / $bitsPerRound);
for ($pass = 0; $pass < $iter; ++$pass)
{
$microStart = microtime(true);
$hash = sha1(mt_rand(), true);
for ($count = 0; $count < $rounds; ++$count)
{
$hash = sha1($hash, true);
}
$entropy .= $microStart . microtime(true);
}
}
$randomStr .= sha1($entropy, true);
}
if ($urandom)
{
@fclose($handle);
}
return substr($randomStr, 0, $length);
}