public function testCreateKey()
 {
     extract(RSA::createKey(512));
     $this->assertInstanceOf('\\phpseclib\\Crypt\\RSA', $privatekey);
     $this->assertInstanceOf('\\phpseclib\\Crypt\\RSA', $publickey);
     $this->assertNotEmpty("{$privatekey}");
     $this->assertNotEmpty("{$publickey}");
     return array($publickey, $privatekey);
 }