Section: New Results

Integrity checking with coupled objects

Participants : Michel Banâtre [contact] , Paul Couderc, Jean-Francois Verdonck.

While the computing and telecommunication worlds commonly use digital integrity checking, many activities from the real world do not benefit from automatic integrity control mechanisms. RFID technology offers promising perspectives for facing this problem, but also raises strong privacy concerns as most of the RFID-based systems rely on global identification and tracking. In 2011, we have designed Ubi-Check to provide an approach aiming at coupling physical objects and enabling integrity control built on local interactions, without the support of a global information system. Ubi-Check led to the development of various novel applications running quite on the same technology. But the possibility of defining hierarchical couplings was lacking.

This is why we have studied and and designed the Ubi-Tree environment in 2012, which strives to deal with those new requirements. Ubi-Tree relies on a structure in which physical objects (also called fragments) are seen as external nodes of a tree that we call coupling tree. External nodes of a tree are called leaves. In the system, internal nodes are called coupling nodes. Each fragment embeds an RFID tag supporting coupling data. Coupling data stores the coupling tree. Each internal node can be checked, which means a lacking, illegally forged or corrupted node can be detected at any depth of a coupling.

Figure 2. Key to a Ubi-Post briefcase

The Ubi-Tree environment has been experimented through a content-oriented security solution for high value shipping: the Ubi-Post briefcase. Sending sensitive documents or parcels over a delivery service can be a hazardous operation. Goods can be picked up by a fake courier, genuine items can be swapped with copies, the parcel may be received or opened by someone else than the supposed recipient and some items can be missing at the delivery time. As some very high value items are sent over such services, security is critical. We proposed the Ubi-Post briefcase system, a pervasive content-oriented security solution for high value shipping based on the Ubi-Tree physical object coupling software and RFID equipment. The aim of a shipping service is to provide transportation of goods from a sender to the recipient, so the system must ensure that the coupling would be handed over to the recipient. For that purpose, coupled tags will carry an identifier corresponding to the recipient as additional data. Then, the only way to unlock a Ubi-Post briefcase is to insert a recipient card which tag ID is the one expected by the coupling (see figure 2 ). The Ubi-Post briefcase embeds the same equipment as the coupling station, plus a battery, an HF near field card reader, and a locking mechanism (see Figure 3 ).

Figure 3. 3D view from the internal components of the Ubi-Post briefcase

We have produced an interface for users to be sure that the association between RFID tag and physical object is the one that is perceived by our coupling software. The key idea was to be able to identify in the right way the RFID tag associated to a physical object when we place one physical object onto the support of the antenna linked to the RFID reader. The position of this object, and the tag associated to this object, in the physical space is determined using a camera coupled with an image recognition algorithm. The result is displayed onto a touch screen. In that way, when we want to couple a set of physical objects, we place sequentially all these objects onto the support of the antenna, and from the image of these objects displayed onto the touch screen we touch those we want to couple and activate the coupling operation. This solution is now fully functional.