Research Exchange: Security For and From GPS

Per Enge [Professor of Aeronautics and Astronautics, Stanford University]

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These days, GPS is used by all of us, and our application space is partially spanned by the following far-flung examples. Several hundred million GPS chip sets were shipped as part of cell phones last year, where they added about $2 to the bill or materials. These will support consumer applications like location specific advertising. The same chip sets will save lives when associated with an emergency call from a distressed citizen. In addition, GPS is included in every new Boeing or Airbus jet, and these receivers cost over $10,000 each. The cost is dominated by the non-recurring cost associated with certifying a receiver for navigation at night or in bad weather.

These GPS applications include location transactions of high value. The value may be economic or safety related. As this trend continues, the conspicuous vulnerabilities of GPS become more important. The GPS signals originate in medium earth orbits. After they have completed their 20,000 kilometer journey to Earth, they have a received signal power of approximately 10^(-16) Watts (-160 dBW). These signals can be readily overwhelmed by inband transmissions from terrestrial sources. This radio frequency interference (RFI) can be scheduled (for military testing), accidental (e.g. harmonics from broadcast television), or malevolent. Malevolent RFI is also known as jamming and is routine for the modern car thief. GPS signals can also be spoofed. In this case, the attacker does not plan to overwhelm the receiver, but rather wishes to introduce misleading location information without detection.

This talk will focus on cures for jamming and spoofing. It will offer two case studies. One describes the impressive effort by the Federal Aviation Administration to secure our airspace against GPS jamming, and research to support that continuous development. The other will talk about a technique to authenticate the provenance of an asserted GPS location.


As always, these talks are free, open to the public and broadcast live on-line at mms:// the day and time of the event. Questions can be sent via Yahoo IM to username: citrisevents. Sponsored by Infineon Technologies. The schedule for the spring semester is at