/**
* powmod using bcmath extension
*/
function _powmodBcmath($x, $y, $mod)
{
if (function_exists('bcpowmod')) {
return bcpowmod($x, $y, $mod);
} else {
if (bccomp($y, 1) == 0) {
return bcmod($x, $mod);
} else {
if (bcmod($y, 2) == 0) {
return bcmod(bcpow(Security_DSA::_powmodBcmath($x, bcdiv($y, 2), $mod), 2), $mod);
} else {
return bcmod(bcmul($x, Security_DSA::_powmodBcmath($x, bcsub($y, 1), $mod)), $mod);
}
}
}
}
