pass secure information from one server to another

Question

The situation is this: A payment is made to one server, and on completion, it must notify another server securely. What I am trying to do is actually quite similar to a notify_url of a payment service. I.E. paypal receives a payment, and then notifies the origin through a long URL.

How does one verify the data being passed. Any useful libraries? Any links to get me started?

Thanks!

Answer 1

HMAC is a good way to ensure that the URL has not been generated by an unauthorized party or tampered with in any way. Here is a simple tutorial.

If the URL (or the content it returns) contains any sensitive information, then you'll also want to make sure that the recipient server is SSL enabled.

And for a further layer of security, you could hard-code the recipient server to reject any connections that aren't from the IP address(es) of your known sender(s).