Helper custom in Symfony

I am developing an application in Symfony 3 and I would like to know what is the best way to create a Helper that can obtain defined parameters. Let me explain:

I have a file of parameters with some keys of an Api defined:

parameters:
    api.public.key: '123456789'
    api.private.key: 'ABCDEFGHI'
    api.timestamp: '1'

Now, I want to make a Helper defined here Utils/ApiHelper.php that can read those parameters for using a function to generate a hash.

I have defined the helper as a service but I do not know how to send the parameters to it.

services:
    api.helper:
        class: AppBundle\Utils\ApiHelper
        public: true