I am developing a cross platform app that can handle payments, the online payment service issued a certificate for my use, thus I have a .pem certificate and within it there is 2 actual certificates and my private key.
The problem is that I can't seem t find how to use it safely, as it has to go in the requests to the web service of the online payment service, therefore I have to include it in my mobile app package, but if anybody opens the package he or she will instantly have access to the private key.
How can I manage this situation? Should I just include it and forget about it as anyway an attacker will have to have valid credit card numbers, or should I create an intermediate web service that can add the certificate?