/**
* Generate a number that lies between 0 and q-1.
*
* @param \phpseclib\Math\BigInteger $q Max number.
*
* @return \phpseclib\Math\BigInteger Generated number.
*/
public static function randomNumber($q)
{
$bytes = strlen($q->toBytes()) + 8;
$ints = $bytes + 1 >> 2;
$cstring = Crypt\Random::String($ints);
$random = '';
for ($i = 0; $i < $ints; ++$i) {
$random .= pack('N', $cstring[$i]);
}
$c = new BigInteger(substr($random, 0, $bytes), 256);
$one = new BigInteger(1);
$result_base = $c->divide($q->subtract($one));
return $result_base[1]->add($one);
}