public function verifyDataSignature ( $data, $consumer_secret, $token_secret, $signature_method, $signature )
	{
		if (is_null($data))
		{
			$data = '';
		}

		$sig = $this->getSignatureMethod($signature_method);
		if (!$sig->verify($this, $data, $consumer_secret, $token_secret, $signature))
		{
			throw new OAuthException2('Signature verification failed ('.$signature_method.')');
		}
	}