# US 9,753,142 B2 · Anti-spoofing in a satellite navigation system > Agents: this data is available as JSON from the patentgrep API and MCP server — see https://patentgrep.com/llms.txt - Number: US 9,753,142 B2 - Document ID: US9753142B2 - Status: Granted - Kind: B2 - Application number: 14/049,646 - Filed: 2013-10-09 - Published: 2015-04-09 - Granted: 2017-09-05 - Earliest claimed: 2013-10-09 - Assignees: Exelis, Inc. - Applicants: Exelis Inc. - Inventors: Michael L. Broussalian - Web page: https://patentgrep.com/patent/US9753142B2 ## CPC - G01S 19/215: {issues related to spoofing} - G01S 19/015: {Arrangements for jamming, spoofing or other methods of denial of service of such systems} - G01S: RADIO DIRECTION-FINDING; RADIO NAVIGATION; DETERMINING DISTANCE OR VELOCITY BY USE OF RADIO WAVES; LOCATING OR PRESENCE-DETECTING BY USE OF THE REFLECTION OR RERADIATION OF RADIO WAVES; ANALOGOUS ARRANGEMENTS USING OTHER WAVES ## Abstract Embodiments are generally directed to anti-spoofing techniques for satellite navigation systems. In general, the anti-spoofing techniques use codeless or semi-codeless tracking of encrypted satellite signals to generate measurements that can be used to perform consistency checks to received non-encrypted signals. The consistency checks will detect if the non-encrypted signal is a genuine satellite signal or a spoofing signal. ## Claims ### Claim 1 A method comprising: receiving, at a receiver, non-encrypted signals and encrypted signals from a plurality of satellites; determining location information for the receiver from the non-encrypted signals to generate non-encrypted location information; executing a semi-codeless technique to determine location information for the receiver from the encrypted signals to generate encrypted location information; and determining, based on the encrypted location information, a difference between the encrypted location information and the non-encrypted location information. ### Claim 2 (depends on 1) The method of claim 1, further comprising: comparing the difference between the encrypted location information and the non-encrypted location information to a predetermined threshold, wherein a difference that is greater than the threshold indicates that the non-encrypted location information is not accurate. ### Claim 3 (depends on 1) The method of claim 1, wherein determining location information for the receiver from the non-encrypted signals comprises: determining position, velocity, and time measurements (PVT) measurements for the receiver using the non-encrypted signals. ### Claim 4 (depends on 3) The method of claim 3, wherein determining location information for the receiver from the encrypted signals comprises: determining PVT measurements for the receiver from a carrier signal associated with the encrypted signals. ### Claim 5 (depends on 1) The method of claim 1, wherein the receiver is a Global Positioning System (GPS) receiver, the non-encrypted signals are Coarse/Acquisition (C/A) code signals, and the encrypted signals are Precision (P) code signals forming P(Y) signals. ### Claim 6 (depends on 1) The method of claim 1, wherein the receiver is a timing receiver. ### Claim 7 An apparatus, comprising: one or more antennas; a receiver coupled to the one or more antennas configured to: receive, via the one or antennas, non-encrypted signals and encrypted signals from a plurality of satellites; determine location information for the receiver from the non-encrypted signals to generate non-encrypted location information; execute a semi-codeless technique to determine location information for the receiver from the encrypted signals to generate encrypted location information; and determine, based on the encrypted location information, a difference between the encrypted location information and the non-encrypted location information. ### Claim 8 (depends on 7) The apparatus of claim 7, wherein the receiver is further configured to: compare the difference between the encrypted location information and the non-encrypted location information to a predetermined threshold, wherein a difference that is greater than the threshold indicates that the non-encrypted location information is not accurate. ### Claim 9 (depends on 7) The apparatus of claim 7, wherein to determine location information for the receiver from the non-encrypted signals, the receiver is configured to: determine position, velocity, and time measurements (PVT) measurements for the receiver using the non-encrypted signals. ### Claim 10 (depends on 9) The apparatus of claim 9, wherein to determine location information for the receiver from the encrypted signals, the receiver is configured to: determine PVT measurements for the receiver from a carrier signal associated with the encrypted signals. ### Claim 11 (depends on 7) The apparatus of claim 7, wherein the receiver is a Global Positioning System (GPS) receiver, the non-encrypted signals are Coarse/Acquisition (C/A) code signals, and the encrypted signals are Precision (P) code signals forming P(Y) signals. ### Claim 12 (depends on 7) The apparatus of claim 7, wherein the receiver is a timing receiver. ### Claim 13 One or more non-transitory computer readable storage media encoded with software comprising computer executable instructions and when the software is executed operable to: receive at a receiver, non-encrypted signals and encrypted signals from a plurality of satellites; determine location information for the receiver from the non-encrypted signals to generate non-encrypted location information; execute a semi-codeless technique to determine location information for the receiver from the encrypted signals to generate encrypted location information; and determine, based on the encrypted location information, a difference between the encrypted location information and the non-encrypted location information. ### Claim 14 (depends on 13) The non-transitory computer readable storage media of claim 13, further comprising instructions operable to: compare the difference between the encrypted location information and the non-encrypted location information to a predetermined threshold, wherein a difference that is greater than the threshold indicates that the non-encrypted location information is not accurate. ### Claim 15 (depends on 13) The non-transitory computer readable storage media of claim 13, wherein the instructions operable to determine location information for the receiver from the non-encrypted signals comprise instructions operable to: determine position, velocity, and time measurements (PVT) measurements for the receiver using the non-encrypted signals. ### Claim 16 (depends on 15) The non-transitory computer readable storage media of claim 15, wherein the instructions operable to determine location information for the receiver from the encrypted signals comprise instructions operable to: determine PVT measurements for the receiver from a carrier signal associated with the encrypted signals.