Systems and methods for providing conditional access to transmitted information

1. A method for controlling access to position information by one or more applications, the method comprising:

decrypting, using a first key, a first set of encrypted position signals received from a network of terrestrial transmitters;

determining position information from the first set of decrypted position signals;

identifying a first set of the position information, wherein the first set of the position information is identified based on a first level of service associated with a first application;

encrypting the first set of the position information using a second key; and

providing the encrypted first set of the position information to the first application.

2. The method of claim 1 , wherein the first set of the position information includes at least one of position coordinates, timing corrections and atmospheric measurements of one or more transmitters from the network of terrestrial transmitters.

3. The method of claim 1 , wherein the method comprises:

computing estimated coordinates of a location of a receiver using the decrypted position signals, wherein the first set of the position information includes the estimated coordinates of the receiver.

4. The method of claim 3 , wherein the decrypted position signals include data that specifies atmospheric measurements at each of the terrestrial transmitters, wherein the estimated coordinates include an altitude coordinate that is computed using the decrypted position signals and at least one atmospheric measurement at the receiver.

5. The method of claim 1 , wherein the method comprises:

computing estimated coordinates of a location of a receiver using the decrypted position signals; and

computing, based on a level of accuracy permitted for the first application, revised coordinates that are based on the estimated coordinates, wherein the revised coordinates are less accurate than the estimated coordinates in specifying the location of the receiver, and wherein the first set of the position information includes the revised coordinates.

6. The method of claim 1 , wherein the method comprises:

identifying a second set of the position information, wherein the second set of the position information is identified based on a second level of service associated with a second application, wherein certain position information included in the first set is not included in the second set;

encrypting the second set of the position information using a third key; and

providing the second set of the position information to the second application.

7. The method of claim 1 , wherein the method comprises:

decrypting, using the first key or a third key, a second set of encrypted position signals received from the network of terrestrial transmitters, wherein the first set of encrypted position signals are received at a first location of the receiver, and the second set of encrypted position signals are receiver at a second location of the receiver;

determining additional position information from the second set of decrypted position signals;

identifying a second set of the additional position information, wherein the second set of the additional position information is identified based on a second level of service associated with a second application;

encrypting the second set of the position information using a fourth key; and

providing the second set of the position information to the second application.

8. The method of claim 1 , wherein the method comprises:

determining, prior identifying the first set of the position information, whether information specifying the first level of service is stored on the receiver;

upon determining that the information specifying the first level of service is not stored on the receiver, accessing a first developer key that is associated with the first application;

sending the first developer key to a server; and

receiving the information specifying the first level of service in response to sending the first developer key to the server.

9. The method of claim 8 , wherein the information specifying the first level of service is included in a first authorized service-level certificate associated with the first application, and wherein the certificate is associated with the developer key.

10. The method of claim 1 , wherein the first level of service specifies a time period during which the second key can be used to encrypt the first set of the position information and any subsequent sets of any subsequent position information.

11. The method of claim 1 , wherein the second key is a session key that is generated after the position signals are decrypted.

12. The method of claim 1 , wherein first application runs on a remote server, and the first set of the position information is provided to the remote server.

13. The method of claim 1 , wherein the method comprises:

determining the first level of service based on parameters that are specified in a first certificate associated with the first application.

14. The method of claim 1 , wherein the method comprises:

scrambling the position information before the position information is sent through an unprotected communication pathway; and

unscrambling the scrambled position information before identifying the first set.

15. The method of claim 1 , wherein the method comprises:

selecting the first key from among a plurality of keys, wherein a CRC field of the encrypted position signals passes check only when the first key is used to decrypt the first set of encrypted position signals; or

selecting the first key from among a plurality of keys, wherein data of the decrypted position signals matches an expected range of values only when the first key is used to decrypt the first set of encrypted position signals; or

selecting the first key from among a plurality of keys, wherein the packet data from the multiple transmitters pass one or more coherency checks only when the first key is used to decrypt the first set of encrypted position signals.

16. The method of claim 1 , wherein the first set of the position information includes position coordinates of different transmitters from the network of terrestrial transmitters.

17. The method of claim 1 , wherein the first set of the position information includes timing corrections from the network of terrestrial transmitters, or the position information specifies measurements of pressure from different transmitters in the network of terrestrial transmitters.

18. The method of claim 1 , wherein the first set of the position information includes position coordinates of one or more transmitters from the network of terrestrial transmitters, timing corrections of the one or more transmitters, or atmospheric measurements taken at a location of the one or more transmitters, the method further comprising:

computing estimated coordinates of a receiver's location using the first set of the position information.

19. The method of claim 1 , wherein the first set of the position information includes estimated times-of-arrival of the position signals that originated from the network of terrestrial transmitters.

20. The method of claim 1 , further comprising:

receiving the first set of encrypted position signals at a receiver, wherein the position signals do not specify the receiver's location; and

estimating the receiver's location using the first set of the position information.

21. A non-transitory computer-readable medium embodying program instructions adapted to be executed to implement a method for controlling access to position information by one or more applications, the method comprising:

decrypting, using a first key, a first set of encrypted position signals received from a network of terrestrial transmitters;

determining position information from the first set of decrypted position signals;

identifying a first set of the position information, wherein the first set of the position information is identified based on a first level of service associated with a first application;

encrypting the first set of the position information using a second key; and

providing the encrypted first set of the position information to the first application.

22. The non-transitory computer-readable medium of claim 21 , wherein the first set of the position information includes at least one of position coordinates, timing corrections and atmospheric measurements of one or more transmitters from the network of terrestrial transmitters.

23. The non-transitory computer-readable medium of claim 21 , wherein the method comprises:

computing estimated coordinates of a location of a receiver using the decrypted position signals, wherein the first set of the position information includes the estimated coordinates of the receiver.

24. The non-transitory computer-readable medium of claim 23 , wherein the decrypted position signals include data that specifies atmospheric measurements at each of the terrestrial transmitters, wherein the estimated coordinates include an altitude coordinate that is computed using the decrypted position signals and at least one atmospheric measurement at the receiver.

25. The non-transitory computer-readable medium of claim 21 , wherein the method comprises:

computing estimated coordinates of a location of a receiver using the decrypted position signals; and

computing, based on a level of accuracy permitted for the first application, revised coordinates that are based on the estimated coordinates, wherein the revised coordinates are less accurate than the estimated coordinates in specifying the location of the receiver, and wherein the first set of the position information includes the revised coordinates.

26. The non-transitory computer-readable medium of claim 21 , wherein the method comprises:

identifying a second set of the position information, wherein the second set of the position information is identified based on a second level of service associated with a second application, wherein certain position information included in the first set is not included in the second set;

encrypting the second set of the position information using a third key; and

providing the second set of the position information to the second application.

27. The non-transitory computer-readable medium of claim 21 , wherein the method comprises:

decrypting, using the first key or a third key, a second set of encrypted position signals received from the network of terrestrial transmitters, wherein the first set of encrypted position signals are received at a first location of the receiver, and the second set of encrypted position signals are receiver at a second location of the receiver;

determining additional position information from the second set of decrypted position signals;

identifying a second set of the additional position information, wherein the second set of the additional position information is identified based on a second level of service associated with a second application;

encrypting the second set of the position information using a fourth key; and

providing the second set of the position information to the second application.

28. The non-transitory computer-readable medium of claim 21 , wherein the method comprises:

determining, prior identifying the first set of the position information, whether information specifying the first level of service is stored on the receiver;

upon determining that the information specifying the first level of service is not stored on the receiver, accessing a first developer key that is associated with the first application;

sending the first developer key to a server; and

receiving the information specifying the first level of service in response to sending the first developer key to the server.

29. The non-transitory computer-readable medium of claim 28 , wherein the information specifying the first level of service is included in a first authorized service-level certificate associated with the first application, and wherein the certificate is associated with the developer key.

30. The non-transitory computer-readable medium of claim 21 , wherein the first level of service specifies a time period during which the second key can be used to encrypt the first set of the position information and any subsequent sets of any subsequent position information.

31. The non-transitory computer-readable medium of claim 21 , wherein the second key is a session key that is generated after the position signals are decrypted.

32. The non-transitory computer-readable medium of claim 21 , wherein first application runs on a remote server, and the first set of the position information is provided to the remote server.

33. The non-transitory computer-readable medium of claim 21 , wherein the method comprises:

determining the first level of service based on parameters that are specified in a first certificate associated with the first application.

34. The non-transitory computer-readable medium of claim 21 , wherein the method comprises:

scrambling the position information before the position information is sent through an unprotected communication pathway; and

unscrambling the scrambled position information before identifying the first set.

35. The non-transitory computer-readable medium of claim 21 , wherein the method comprises:

selecting the first key from among a plurality of keys, wherein a CRC field of the encrypted position signals passes check only when the first key is used to decrypt the first set of encrypted position signals; or

selecting the first key from among a plurality of keys, wherein data of the decrypted position signals matches an expected range of values only when the first key is used to decrypt the first set of encrypted position signals; or

selecting the first key from among a plurality of keys, wherein the packet data from the multiple transmitters pass one or more coherency checks only when the first key is used to decrypt the first set of encrypted position signals.

36. The non-transitory computer-readable medium of claim 21 , wherein the first set of the position information includes position coordinates of different transmitters from the network of terrestrial transmitters.

37. The non-transitory computer-readable medium of claim 21 , wherein the first set of the position information includes timing corrections from the network of terrestrial transmitters, or the position information specifies measurements of pressure from different transmitters in the network of terrestrial transmitters.

38. The non-transitory computer-readable medium of claim 21 , wherein the first set of the position information includes position coordinates of one or more transmitters from the network of terrestrial transmitters, timing corrections of the one or more transmitters, or atmospheric measurements taken at a location of the one or more transmitters, the method further comprising:

computing estimated coordinates of a receiver's location using the first set of the position information.

39. The non-transitory computer-readable medium of claim 21 , wherein the first set of the position information includes estimated times-of-arrival of the position signals that originated from the network of terrestrial transmitters.

40. The non-transitory computer-readable medium of claim 21 , further comprising:

receiving the first set of encrypted position signals at a receiver, wherein the position signals do not specify the receiver's location; and

estimating the receiver's location using the first set of the position information.