/**
* Generate modulated number
*
* Generates a number that lies between 0 and q-1
*
* @access public
* @static
* @staticvar MathBigInteger $one Constant one
* @param MathBigInteger $q Modulation
* @return MathBigInteger Generated number
*/
public static function randomNumberMod($q)
{
// do a few more bits than q so we can wrap around with not too much bias
// wow, turns out this was actually not far off from FIPS186-3, who knew?
// FIPS186-3 says to generate 64 more bits than needed into "c", then to do:
// result = (c mod (q-1)) + 1
static $one;
if (!isset($one)) {
$one = new MathBigInteger(1);
}
$c = self::_os2ip(self::_random(strlen($q->toBytes()) + 8));
$result_base = $c->divide($q->subtract($one));
return $result_base[1]->add($one);
}
