Example Applications - RFID: Fundamentals and Applications in Contactless Smart Cards and Identification - page 360

Figure 13.31 Pigeon upon arrival at its own pigeonry. Upon the pigeon's entry, the transponder
in the ring is read (reproduced by permission of Legic Identsystems, CH-Wetzikon)

To solve the problem of timing, the pigeons are fitted with rings that incorporate a
read-only transponder based upon a glass transponder. As the pigeons are loaded onto
the transporter for transport to the release site, the serial numbers of the transponders
are read to register the animals for participation in the race. Upon the pigeon's arrival
at its home pigeonry a reader installed in the pigeonhole records the serial number
and stores it, together with the precise arrival time, in a portable control unit. Judging
takes place by the reading of the devices at the operating point (Figure 13.31).
However, the ingenuity of some of the breeders was greatly underestimated when
this system was first introduced. It was not long before some breeders were not only
able to read the transponder codes from the pigeon ring, but could also fool the reader
using a simulation device in the home pigeonry. The technology involved was fairly
simple — all that was required was an extremely simple read-only transponder, whose
'serial number' could be altered using external DIP switches. Thus, some breeders
were able to significantly accelerate the 'flight speeds' of their champions.
An effective measure to protect against such attempts at fraud is the incorporation of
an additional writable EEPROM memory into the transponder. The memory size is just
1 byte to keep the chip size and cost of circuitry low (Figure 13.32). Before the start,
a previously determined random number, for which there are 2 8 = 256 possibilities, is

written to this byte in the transponder at the headquarters. It is crucial that the breeder
does not have access to his bird while it is being transported to the release site after the
transponder has been programmed. This prevents the random number from being read.
When the pigeon reaches its home pigeonry, its arrival is confirmed electronically. The
time, together with the transponder code and the secret random number are stored.
When the records are evaluated at the headquarters, the random number read upon
arrival is compared with the number programmed at the start. The measured times are
only validated if the two figures are identical, otherwise it is assumed that an attempted
fraud has taken place.
The procedure described is clearly adequate to successfully prevent attempted fraud.
With 256 possibilities for the random number the probability that this will be guessed
correctly in a single attempt is only 0.4%.
In order to keep the weight and dimensions of the pigeon transponder low, glass
transponders are used in this application, which are cast into a plastic ring. These plastic