Wireless signal validation using an independent wireless data link
For validation of wireless signals, a wireless receiver receives a validation signal that includes information from a target signal. By using digital signature, message authentication code (MAC), and/or hashing, the validation signal is verified to be from a trusted source. By comparing the information from the verified validation signal with the target signal, the target signal is confirmed to be genuine or not a spoofing signal. In one approach, the validation signal is provided from a different transmission source than the target signal. In another approach, modulation estimation rather than known modulation is used as the information for the validation signal for comparison with the target signal despite not knowing the spread pattern of the coding. In yet another approach, a one-way function is used to generate a pseudorandom code to spread a first component of the a first signal below the noise floor. The input to the one-way function is a second component sent at a time later than the time.
1 . A method for validation of wireless signals, the method comprising:
receiving wirelessly, at a receiver, a target signal from a first source;
receiving wirelessly, at the receiver, a validation signal from a second source different than the first source, the validation signal comprising (i) a digital signature or message authentication code of a composite of (a) data source bits from the target signal and (b) hash chain data and (ii) the data source bits;
verifying the validation signal with a digital signature, message authentication code, or reverse hash chain check; and
validating the target signal from the verified validation signal,
wherein receiving the target signal from the first source comprises receiving the target signal from a first low earth orbit satellite, and
wherein receiving the validation signal from the second source comprises receiving the validation signal from a second low earth orbit satellite.
2 . The method of claim 1 wherein receiving the target signal comprises receiving the target signal from a first satellite, and wherein validating comprises validating the first source as a first satellite.
3 . The method of claim 1 wherein receiving the target signal comprises receiving the target signal from a global navigation satellite system.
4 . The method of claim 1 wherein receiving the target signal comprises receiving the target signal from a geosynchronous earth orbit satellite.
5 . The method of claim 1 wherein the validation signal includes information for the target signal and/or first source as the data source bits, and wherein validating comprises comparing the information with the target signal.
6 . The method of claim 5 wherein the validation signal comprises a composition of (a) the information for the target signal and/or first source and (b) the hash chain data as a hash chain link in a reverse hash chain and wherein verifying comprises verifying with the digital signature or the message authentication code.
7 . The method of claim 1 wherein receiving the validation signal comprises receiving the validation signal where the validation signal is based on the target signal received in a spoof-free region or data received on a wired data link.
8 . The method of claim 1 wherein the first source comprises a GNSS satellite, wherein the validation signal comprises an estimate of code bits from the first source, and wherein validating comprises determining that a comparison of the estimate of the code bits matches the target signal.
9 . The method of claim 8 wherein the first source is a satellite from a global navigation satellite system and the estimate of the code bits is an estimate of modulation initially unknown to the receiver, and wherein determining comprises determining the match where a correlation peak of the estimate with the target signal.
10 . The method of claim 1 wherein the first source comprises a terrestrial transmitter and the target signal comprises a signal of opportunity, wherein the validation signal is formed from a baseband and/or intermediate frequency representation of the target signal, and further comprising correlating the target signal with the baseband and/or intermediate frequency representation from the validation signal and determining location based on the correlating.
11 . The method of claim 1 wherein the first source is a cellular base station, wherein the validation signal includes first information, and wherein validating comprises comparing the first information to second information in the target signal.
12 . The method of claim 1 wherein the validation signal is formed from the digital signature or message authentication code of another digital signal or another message authentication code of values for a plurality of parameters of the target signal, wherein verifying comprises comparing the other digital signal or the other message authentication code, and wherein validating comprises comparing the values for the plurality of parameters extracted from the other digital signal or the other message authentication code with characteristics of the target signal or the first source.
13 . The method of claim 1 wherein the validation signal is formed from the digital signature or message authentication code of another digital signal or another message authentication code of global positioning system (GPS) subframe data, wherein verifying comprises comparing the other digital signal or the other message authentication code, and wherein validating comprises comparing the GPS subframe data extracted from the other digital signal or the other message authentication code with GPS subframe data from the target signal.
14 . The method of claim 1 wherein receiving the validation signal comprises receiving from the second source out-of-band from the first source.
15 . The method of claim 1 wherein receiving the validation signal comprises receiving the validation signal as a second factor authentication where the second source is in a different constellation or communications network than the first source.
16 . The method of claim 1 wherein the first and second sources are transmitters of a same constellation.
17 . The method of claim 1 wherein receiving the target signal comprises receiving the target signal in a vehicle operating autonomously.
18 . A system for wireless validation, the system comprising:
a receiver configured to receive a first wireless signal from a first network and a second wireless signal from a second network different than the first network; and
a signal processor configured to validate the first wireless signal from content of the second wireless signal, the content comprising code symbols, time, and/or location corresponding to the first wireless signal, the validation comprising a direct comparison of the code symbols, time, and/or location,
wherein the first network comprises a first low earth satellite system, and the receiver is configured to receive the first wireless signal from the first low earth orbit satellite system, and
wherein the second network comprises a second low earth orbit satellite system, and the receiver is configured to receive the second wireless signal from the second low earth orbit satellite system.
19 . The system of claim 18 wherein the signal processor is configured to validate the second wireless signal with a reverse hash, digital signature, or message authentication code, and wherein the signal processor is configured to validate the first wireless signal with the content once the second wireless signal is validated.
20 . The system of claim 18 wherein the signal processor is configured to extract the content of the second wireless signal with a hash chain link of a reverse hash chain.
21 . The system of claim 18 wherein the content comprises the first wireless signal or data characterizing the first wireless signal or the first network.
22 . The system of claim 18 wherein the first network comprises a global navigation satellite system, cellular communications system, a mobile communications system, a vehicle-to-vehicle system, or a terrestrial broadcast system, and the second wireless signal is out-of-band of the first wireless signal.
23 . The system of claim 18 wherein the second wireless signal comprises a digital signature or message authentication code of a digital signature or message authentication code of the content.
24 . A system for wireless validation, the system comprising:
a reference receiver configured to receive first wireless signals or data characterizing the first wireless signals;
a signal processor configured to generate a first digital signature or message authentication code from the first wireless signals or the data, generate a second digital signature or message authentication code from the first digital signature or message authentication code and a hash chain link, and generate a validation signal from the second digital signature or message authentication code and the first digital signature or message authentication code; and
a first transmitter configured to wirelessly transmit the validation signal to a user receiver configured to receive the validation signal from the first transmitter and to receive the first wireless signal from a second transmitter of a different communications network than the first transmitter,
wherein the first transmitter is part of a fir low earth orbit satellite communications system, and the user receiver is configured to receive the validation signal from the fir low earth orbit satellite system, and
wherein the second transmitter is part of a second low earth orbit satellite communications system.
25 . The system of claim 24 wherein the reference receiver is configured to receive the data characterizing the first wireless signals on a wired link from a generator of the first wireless signals.
26 . The system of claim 24 wherein the second transmitter is part of a global navigation satellite system.
27 . The system of claim 24 wherein the second transmitter is a cellular transmitter.