public function getParameters()
    {
        if (null === $this->getParameter('PBX_HMAC')) {
            $this->setParameter('PBX_TIME', date('c'));
            $this->setParameter('PBX_HMAC', strtoupper($this->computeHmac()));
        }

        $resolver = new ParameterResolver($this->globals['currencies']);

        return $resolver->resolve($this->parameters);
    }