/**
* verify using gmp extendsions
*/
function _verifyByGmp($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);
$p = gmp_init($p);
$q = gmp_init($q);
$g = gmp_init($g);
$pubKey = gmp_init($pubKey);
$s1 = Security_DSA::_bindecGmp($r_sig);
$s2 = Security_DSA::_bindecGmp($s_sig);
$w = gmp_invert($s2, $q);
$hash_m = gmp_init('0x' . sha1($message));
$u1 = gmp_mod(gmp_mul($hash_m, $w), $q);
$u2 = gmp_mod(gmp_mul($s1, $w), $q);
$v = gmp_mod(gmp_mod(gmp_mul(gmp_powm($g, $u1, $p), gmp_powm($pubKey, $u2, $p)), $p), $q);
return gmp_cmp($v, $s1) == 0;
}
