/**
* Calculates the signature for the request
*
* @param array $params
*
* @return string
*/
protected function buildSignature(array $params)
{
$template = "GET\nwebservices.amazon.%s\n/onca/xml\n%s";
return Util::buildSignature(sprintf($template, $this->configuration->getCountry(), implode('&', $params)), $this->configuration->getSecretKey());
}