Interactive device network registration protocol

In a network connected to an optical sensing device and a registration server, a method for registering the optical sensing device with the registration server and using the optical sensing device, including the steps of:

• installing a secret key and a public unique identifier in non-volatile memory in the optical sensing device and in a database of the registration server, before the optical sensing device is connected to the network;
• when the optical sensing device is connected to the network, authenticating the optical sensing device at the server by verifying the optical sensing device's encryption, using the secret key, of a challenge message;
• if the authentication succeeds, registering the optical sensing device in the database of the registration server;
• and
• using the optical sensing device to capture a sequence of time-stamped positions of the optical sensing device relative to a surface, wherein the surface includes coded data that is read by the optical sensing device.