SignedRequest
A signed request is a great way to pass data from one source to a target in a way that can be trusted and tamper proof. A Payload can be signed with use of a secret. If both source and target servers share the same secret than they can issue a request that can be trusted. Companies such as Facebook and Salesforce use these to pass information about a user's session to their app canvas iframes, they could also be used to create urls whose params cannot be tampered with.