/**
* verify using bcmath extension
*/
function _verifyByBcmath($message, $sig, $sigKeys)
{
$p = $sigKeys['p'];
$q = $sigKeys['q'];
$g = $sigKeys['g'];
$pubKey = $sigKeys['pub_key'];
list($r_sig, $s_sig) = explode(':', $sig);
$r_sig = base64_decode($r_sig);
$s_sig = base64_decode($s_sig);
$s1 = Security_DSA::_bindecBcmath($r_sig);
$s2 = Security_DSA::_bindecBcmath($s_sig);
$w = Security_DSA::_invertBcmath($s2, $q);
$hash_m = Security_DSA::_hexdecBcmath(sha1($message));
$u1 = bcmod(bcmul($hash_m, $w), $q);
$u2 = bcmod(bcmul($s1, $w), $q);
$v = bcmod(bcmod(bcmul(bcmod(Security_DSA::_powmodBcmath($g, $u1, $p), $p), bcmod(Security_DSA::_powmodBcmath($pubKey, $u2, $p), $p)), $p), $q);
return bccomp($v, $s1) == 0;
}
