Secure information transfer based on global position   

Abstract: Secure communication of information is effected from a first party to a second party when the first party knows its own global location and the global location of the second party, and employs what essentially is an undiscoverable code signal that is broadcast to, and received by, both the first and the second parties. The first party securely communicates information to the second party by modifying the code signal with the information that is to be communicated and sends the modified code signal to the second party. Illustratively, the code signal is related to the Y component of a GPS signal.

This application is a continuation of U.S. patent application Ser. No. 12/231,094, which was filed on Aug. 29, 2008 which is a continuation in part of U.S. patent application, Ser. No. 12/012,327, which was filed on Feb. 2, 2008.

BACKGROUND OF THE INVENTION

When information needs to be communicated in a secure manner one typically turns to cryptographic techniques. It is generally recognized that with many cryptographic techniques the encrypted data can be recovered by an adversary, but only if the adversary has sufficient resources (e.g., computing power) and sufficient time. Most users are satisfied when a method is secure “enough,” meaning that the time, effort, or expense to recover the data embedded in an encrypted message is too great to make the data useful to an adversary.

With the above in mind, cryptographic techniques usually depend on encryption and decryption keys being in possession of the communicating parties. Aside from the concern about the inherent security of message encrypted with a particular method, the biggest concern is with the secure creation, distribution and maintenance of the keys.

SUMMARY

An advance in the art is achieved with a method that implements secure transmission of information from one party to another without the need for cryptographic keys but, rather, based on unique geographic attributes such as position as well as time. More specifically, secure communication of information is effected from a first party to a second party when the first party knows its own global location and the global location of the second party, and employs a code signal that is broadcast to, and received by, both the first and the second parties. The first party securely communicates information to the second party by modifying the code signal with the information that is to be communicated and sends the modified code signal to the second party. The code signal that is received by the first party and is used to convey information to the second party need not to be actually known to either of the parties, and from the standpoint of secure communication it is advantageous for the broadcasted code signal (and the corresponding related received signals) to not be known to either of the parties and to be essentially impossible for the parties to discover. The signal that is employed in the disclosed illustrative example is related to the Y component of a GPS signal. Other wireless sources that are modified to include a signal like the Y component of the GPS signal can also be employed.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 depicts a first unit that securely transmits information without the use of cryptographic keys;

FIG. 2 shows some of the processing within processor 40 of FIG. 1; and

FIG. 3 depicts some of the processing within a unit that receives the signal transmitted by the FIG. 1 unit.

DETAILED DESCRIPTION

U.S. patent application Ser. No. 12/012,327 discloses an approach whereby a first device, at location x, can verify an assertion by a second device, at location y, as to the global position of the second device. The disclosure presented an illustrative embodiment that is based on the Global Positioning System (GPS) but the principles disclosed therein are broader and are not limited to the GPS. For examples, they can be readily applied to the other global navigation satellite systems being developed and deployed worldwide.

To assist the reader in understanding the instant invention without having to read the aforementioned application, the following repeats a significant portion of the mathematical underpinnings presented in the 12/012,327 application. It should be kept in mind that here, as well, the principles of the disclosed invention are broader than the illustrative example that uses the GPS.

FIG. 1 shows unit 100 that belongs to Remote Device B, which simultaneously receives a number of GPS satellite signals on frequency L1, where the signal transmitted by satellite n can be expressed as

Stransmittedn=AnDn(t)xCn(t)cos(2π(fL1)t+φ1)+BnDn(t)xYn(t)sin(2π(fL1)t+φ1)  (1)

where Dn(t) is the data signal of satellite n, xCn(t) is a code signal assigned to satellite n that is publicly known, xYn(t) is a code signal assigned to satellite n that is not publicly known, fL1 is the frequency of the carrier, and φ1 is the phase of the carrier relative to the beginning of the data and code signals. Unit 100 is the party that wishes to send information to a remote unit 200 without the use of cryptographic keys.

A GPS receiver receives a signal corresponding to the sum of the signals of the individual satellites. The receiver can engage in the processing of signals as if all of the possible satellites are present but, of course, some of the satellites are not within range of the GPS receiver\'s antenna (i.e., not detectible) so the processing results for those satellites are not viable. In other words, the signal arriving at the FIG. 1 antenna corresponds to

∑ n = 1 K  [ A n  D n  ( t )  x C n  ( t )  cos  ( 2   π   ( f L   1 )  t + ϕ 1 ) + B n  D n  ( t )  x Y n  ( t )  sin  ( 2   π  ( f L   1 )  t + ϕ 1 ) ] + Noise ( 1  a )

where K is the number of satellites that are within view of the antenna.

The following analysis follows the signal of only one satellite and, for sake of simplicity superscript n is omitted from the equations. The fact that other satellite signals exist is addressed later.

The transmitted signal is subjected to transit time delay before reaching the receiver, and the signal that is received by a first receiver\'s antenna experiences a Doppler frequency shift, fD, due to the satellite\'s movement in its orbit and possible receiver motion. Also, the transmitter and the receiver do not have a common clock, which means that even when the transmitter and the receiver clocks are at identical frequency, there is a phase difference between them. To make the equations more general, one might assume that there is a time shift (the transitions are not fully aligned) between the AD(t)xC(t) and the BD(t)xY(t) , so the signal received at the first receiver can be expressed as