A network including an optical sensing device, and a registration server, wherein a secret key and a unique public identifier are installed in the optical sensing device and in a database of the registration server; wherein the optical sensing device is adapted to communicate with the registration server; wherein, the registration server is adapted to authenticate the optical sensing device when the optical sensing device is connected to the network by verifying the optical sensing device's encryption, using the secret key, of a challenge message; wherein, if the authentication succeeds, the optical sensing device is registered in the database of the registration server; wherein the optical sensing device is adapted to capture a sequence of time-stamped positions of the optical sensing device relative to a surface including coded data.