1. A method for an intermediary device to provide security between a client and server via state signing of resources controlled by policy, the method comprising the steps of: (a) intercepting, by a device between a client and a server, a response from the server to a request of the client, the response comprising a plurality of application data items; (b) determining, via a policy, one or more application data items of the plurality of application data items to sign; (c) generating, by a state signer responsive to the policy, a signature for each of the determined one or more application data items; and (d) transmitting, by the device, to the client in response to the request, a modified response having the signed one or more application data items.