/**
* EMSA-PKCS1-V1_5-ENCODE
*
* See {@link http://tools.ietf.org/html/rfc3447#section-9.2 RFC3447#section-9.2}.
*
* @access private
* @param String $m
* @param Integer $emLen
* @return String
*/
function _emsa_pkcs1_v1_5_encode($m, $emLen)
{
$h = $this->hash->hash($m);
if ($h === false) {
return false;
}
// see http://tools.ietf.org/html/rfc3447#page-43
switch ($this->hashName) {
case 'md2':
$t = pack('H*', '3020300c06082a864886f70d020205000410');
break;
case 'md5':
$t = pack('H*', '3020300c06082a864886f70d020505000410');
break;
case 'sha1':
$t = pack('H*', '3021300906052b0e03021a05000414');
break;
case 'sha256':
$t = pack('H*', '3031300d060960864801650304020105000420');
break;
case 'sha384':
$t = pack('H*', '3041300d060960864801650304020205000430');
break;
case 'sha512':
$t = pack('H*', '3051300d060960864801650304020305000440');
}
$t .= $h;
$tLen = strlen($t);
if ($emLen < $tLen + 11) {
user_error('Intended encoded message length too short', E_USER_NOTICE);
return false;
}
$ps = str_repeat(chr(0xff), $emLen - $tLen - 3);
$em = "{$ps}{$t}";
return $em;
}
/**
* DSA verify
*
* @param string $message message
* @param string $hash_alg hash algorithm
* @param MathBigInteger $r r
* @param MathBigInteger $s s
* @param MathBigInteger $p p
* @param MathBigInteger $q q
* @param MathBigInteger $g g
* @param MathBigInteger $y public key
* @return bool
*/
public static function verify($message, $hash_alg, $r, $s, $p, $q, $g, $y)
{
$hash = new CryptHash($hash_alg);
$hash_m = new MathBigInteger($hash->hash($message), 256);
$w = $s->modInverse($q);
$hash_m_mul = $hash_m->multiply($w);
$u1_base = $hash_m_mul->divide($q);
$u1 = $u1_base[1];
$r_mul = $r->multiply($w);
$u2_base = $r_mul->divide($q);
$u2 = $u2_base[1];
$g_pow = $g->modPow($u1, $p);
$y_pow = $y->modPow($u2, $p);
$g_pow_mul = $g_pow->multiply($y_pow);
$g_pow_mul_mod_base = $g_pow_mul->divide($p);
$g_pow_mul_mod = $g_pow_mul_mod_base[1];
$v_base = $g_pow_mul_mod->divide($q);
$v = $v_base[1];
return $v->compare($r) == 0;
}