For example, the power of passive tags is too weak and the memory too small to incorporate the regular cryptography to secure them from eavesdropping and jamming. And while the active tags are battery-operated and have larger memory, and scanning area, the power of these tags is not strong enough for the regular cryptography to work properly.
A promising alternative to cryptography is ultra wideband (UWB) modulation. Dong S. Ha, and Patrick Schaumont spoke at the IEEE RFID 2007 Conference about how this type of modulation can be used to implement the link from RFID tags to readers. As they discussed, this technology, still being developed, allows for the use of relatively simple ciphers, and UWB is more secure against interference than narrowband.
Tag Signal Interference
Signal interference with RFID tags can result from improper antenna orientation in the tags and close proximity of readers. The challenge is to detect signal interference between tags.
Let's suppose a shopper places RFID-tagged products in a shopping cart in a random orientation. Signal interference occurs when the signals from the antenna in some tags interfere with the signals from the antenna in other passive tags on products. As a result, when your shopper proceeds to checkout, the reader at the checkout counter might not be able to read all the tags in the cart. This means that the tagged items in the shopping cart must be taken out and placed on the checkout counter for proper alignment of the items' orientation before the tags on these items can be adequately re-scanned.
Even if the tagged items are placed in a proper orientation order in the cart to prevent signal interference at checkout, mobile RFID handheld readers (e.g., personal readers used by shoppers as they move about the store) used in close proximity to other readers could garble data while scanning the tags. The radio frequency field generated by one reader used to scan the items in one cart may overlap the field of another reader used to scan different items in a second cart that happens to be in close proximity to the first cart.
To alert the shopper of the read tag interference, these mobile readers could include an alert mechanism that would be able to change color from green to red when signal interference is detected due to overlapping scanning areas caused by the proximity of another shopper's reader. When the red color blinks, a shopper would move away from the overlapping area until the alert stops blinking or turns green.
Not Enough Room Here!
Active RFID tags give rise to another signal interference issue. The challenge here is to mitigate the risks of signal interference due to improper antenna orientation, insufficient numbers of antennas, improper positioning and inadequate reading area.
As you may know, an RFID reader cannot communicate with an active RFID tag that is oriented perpendicular to the reader antenna. With active tags and readers, unlike with passive tags, a minimum of one antenna must be located in one zone. Although several antennas enable more accurate tag positioning to allow for greater reading area, improper positioning due to reflections from walls and equipment can adversely affect the transmission. Tags that are not located at the correct horizontal or vertical levels in buildings also affect transmission quality.
Canus, a maker of goat's milk soap, offers a good example of how it resolved the signal interference by changing the positioning and orientation of the antenna. Its docking door allowed only three antennas to be set up, but the third antenna did not allow enough reading area. Adjustments were made to this antenna by changing its orientation and position to provide a greater reading area, and a fourth antenna was added to ensure that a tag can be read regardless of its location on the pallet.
RFID technology offers great promise for improving supply chain efficiencies, including through store-level deployments. However, as the examples above illustrate, companies that are serious about leveraging this still-emerging technology must take into consideration the various security issues inherent to RFID.