Fishing Vessel Monitoring Systems: Past, Present and Future

VMS: Past, Present and Future 26
reference for maritime navigation in general, and VMS and other tracking
applications in particular, in clear preference to GPS.
4.6.1 Multiple service levels
The Galileo system will offer three levels of service, all of which can be of interest
to entities planning, and operating secure tracking systems. The most secure
approaches will take advantage of the characteristics of each of the three levels
of service proposed for the Galileo system: the open service, safety-of-life
service, and commercial service. On each step of this ascending ladder, the
level of security will become increasingly reliable. Indeed, at the level of
commercial service, it may well be close to inviolable.
The Galileo open service presents capabilities similar to those of GPS, albeit with
the addition of a 250 bit-per-second channel that transmits system integrity data.
Consequently, the integration of samples of this data into positions calculated
with a Galileo receiver would provide a level of assurance that the position
received is the result of a calculation using real Galileo signals.
4.6.2 Levels of difficulty
It should be pointed out that the security of such an approach would be less than
total. This is because, theoretically, it would be possible to integrate data from
the security channel into a simulated Galileo navigation signal. Still, as it would
be necessary to do this in real time, generation of the falsified signal would
require a much higher degree of difficulty, with corresponding increased costs
and the ever-present possibility of making an error in transmission that would
raise suspicions as to data integrity. In addition, proprietary signal processing by
the terminal would further increase the complexity. In any case, such a system
would be a significant improvement over what is currently available and would
have the advantage of being based upon an openly available, free-of-charge
service.
With the safety-of-life service, and its characteristics that are Galileo specific,
verification of the authenticity of retransmitted position data becomes more
assured. It is beginning at this level that the Galileo integrity data channel is
encrypted for decoding only by registered, identified users, thus making it a more
solid platform for data verification. Position data based upon this encrypted
signal, combined with the identity key of the user who has decrypted it, would
provide a level of technical difficulty and cost orders of magnitude superior to the
unencrypted signal of the open service.
The Galileo commercial service provides a 500 bit-per-second communications
channel from satellite to receiver that transmits user-defined data. There is one
such channel per satellite, and it must be shared amongst users. The ability to
transmit, for example, random data to users and to create position reports based