GPS 2.0: Aerospace Corp. Launches Second Draft of GPS | Hacker News Reader

GPS 2.0: Aerospace Corp. Launches Second Draft of GPS

breakingdefense.com

126 pointshackuser30 comments

Nextgen GPS is this: https://en.m.wikipedia.org/wiki/GPS_Block_IIIA

(GPS 2.0 appears to just be a term made up by the author.)

More interesting than this is https://en.m.wikipedia.org/wiki/Real_Time_Kinematic , which uses no extra transmit hardware compared to normal GPS, but can provide mm accuracy. (In practice, it often requires multiple cooperating receivers, but current research is finding ways to make this work practically in single-receiver handheld devices like phones.)

This technique has gotten thousands of times cheaper in recent years (now around $150 for a receiver, according to a talk I recently attended) and should soon be cheap enough for consumer electronics.

This works anywhere and doesn't require supplementary external hardware like Wi-Fi.

There is an external component to this that provides the corrections. Did you read https://en.m.wikipedia.org/wiki/Real_Time_Kinematic#Practica.... It explains the corrections sent either via CORS or VRS.

No, it doesn't work anywhere. It only works where you have line of sight to at least 4 satellites, preferably 5. Indoor positions and positions in urban canyons will not be anywhere near that good.

And you still need the carrier grade corrections, withing 10 to 25km of the rover receiver.

There are growing amounts of free/open correction points/towers. If you're lucky, you might be within 25km of one.

Can anyone find where they got "[GPS had] its most accurate day ever last week" from? All sites about GPS accuracy seem to be down and I can find no news sources mentioning a most accurate day at any point in time.

Edit: a bit further on they mention it in more detail: "It had its “best day ever” on Monday, generating signals with an an average global accuracy of .38 meters." but once again no source.

I'm not sure, I did find some other cool graphs though...

Real-time GPS SPS (Standard Positioning Service) PDOP (Position Dilution of Precision): currently shows 1-2 meters precision worldwide - http://www.nstb.tc.faa.gov/RT_SPSPDOP.htm

24 Hr Max PDOP: http://www.nstb.tc.faa.gov/24Hr_MaxPDOP.htm

It's sourced from an executive vice president of Aerospace Corp. It would make sense that he might know about it from non public sources.

This page is showing up completely blank for me.

Cache: http://webcache.googleusercontent.com/search?q=cache:tsK9lnR...

Adblock issue, I've fixed.

https://hg.adblockplus.org/easylist/rev/3594df2e77f5

Cool, thanks!

I think this is a great proposal. Even so, I'm curious why there needs to be a formal process for the use of many sources in localization. It seems to me that anyone making a localization device (i.e. Apple or Samsung making phones) could add inertial information, cell tower locations, and more to give great location info.

I was a little underwhelmed, myself. Apple absolutely does a bit of this now.

  Depending on your device and available services, Location Services
  uses a combination of cellular, Wi-Fi, Bluetooth, and GPS to determine
  your location. If you're not within a clear line of sight to GPS
  satellites, your device can determine your location using crowd-
  sourced Wi-Fi and cell tower locations or iBeacons.

https://support.apple.com/en-us/HT203033

On the surface this sounds good until you realize that there is a pretty big group of people that started using iPads, etc. with boating navigation and charting app. Pilots too I think. Used to be you could tell when you had a location fix using a GPS, especially when I wifi was turned off. Now my iPad magically gets a location fix even when in airplane mode and I have no idea how or if I can trust it enough for something critical. This all started changing in iOS 8 or 9. Really wish Apple would expose more details to app developers on what type of fix an iDevice was using.

I couldn't agree more that devices don't expose enough detail about a GPS position. It sounds like you solved your problem, though. Airplane mode turns off cell and wifi radios, but leaves GPS alone so it's the only thing left to read position from.

I occasionally use an app called GPS Data on planes to check what speed and altitude I am are travelling. It has a tick indicator that flashes when update is received. It usually doesn't flash if I am too far from the window or can't get a fix.

The APIs provide enough detail:

https://developer.apple.com/library/ios/documentation/CoreLo...

Well, the article is scant on detail, but the posture seems to be not inventing something fundamentally new but rather unifying and standardizing the best of what people are already doing.

Anyone able to compare GPS 2.0 to other systems used by China, Russia, etc.?

The "GPS 2.0" label used in the article is a bit of a misnomer I think, and possibly just something the author came up with. There is no radically new satellite navigation system described, just some rather superficial mentions of the need for alternative electronic navigation aids to augment satellite navigation (Loran, inertial sensors etc), which are not limited, or directly related, to GPS.

The closest thing to bear a "next gen" GPS label is the new block IIIA satellites, sometimes (officially) referred to as GPS III.

For civilian users, the most notable change in block III is that there will be a signal L2C available on the L2 frequency. With 2 frequencies, you can calculate ionospheric delay, resulting in better accuracy and resilience. Before this, L2 only carried the encrypted military Y code (but L2 could still be used for carrier phase tracking, so industrial non-military GNSS receivers could still make some use of it).

There will also eventually be an improved (backward-compatible) signal on the L1 frequency, and even a 3rd signal on L5. There fundamental system remains the same though, this is more of an evolution than a revolution. E.g, L2C is already available on some block II satellites. For military uses, there are some other interesting changes in block III, notably a new military signal M with a spot-beam antenna that can target a limited area, which is pretty cool.

Russia's GLONASS satellites evolve similarly, with the new 3rd gen K satellites getting more frequencies etc, and using CDMA just like GPS (previously the GLONASS signals used FDMA, i.e. each visible satellite used a different frequency slot). Galileo and BeiDou are also quite similar, but BeiDou is notable for using geostationary and inclined geostationary satellites in addition to regular medium earth orbit satellites (essentially to get improved coverage in Asia). A possibly interesting feature of Galileo is that there may be a "commercial service" signal, i.e. that non-navigational data may be broadcast via the Galileo satellites.

I for one would like to take advantage of the slow deployment of L2C and L1C to change the payload. The program delay is potentially an opportunity to add cryptographically strong authentication to the signal structure. The greatest near-term threat to GPS isn't jamming as mentioned in the article, its spoofing. Strong authentication is the most promising antispoofing defense, and the growing commercial drone industry is going to need it.

You seem to know a lot about this and it always interested me.

How does current GPS prevent from spoofing. My understanding is that only military GPS signals are encrypted. If so, how strong is the encryption? What type it is?

It's not so much that the military signal (ranging code) is encrypted, per se, but it uses a DRNG for which the parameters are kept secret.

To be able to spoof GPS, you need to be able to duplicate the ranging code for a given satellite. This is easy for civilian GPS, where the code repeats ~1000 times/sec and the details are public; much harder for military code where it repeats 1 time/week and the parameters are secret.

You can still jam either one, though, just by overwhelming appropriate frequencies with noise. This is what the spot beam in newer satellites is for -- getting more power to areas of conflict to make the signal harder to jam.

> but it uses a DRNG for which the parameters are kept secret

A standard block cipher running in CTR mode would provide the same functionality. So I don't think its wrong to say that the signal is encrypted.

By this logic, crypt(3) creates encrypted (rather than hashed) passwords, because it can be implemented with DES.

The civilian C/A code isn't protected at all. A modern spoofing attack works by initially providing the target with the same GPS signal that the target is already reading. By "same" I mean phase-correct for that target in that position and time. Then the magnitude of the spoof signal is increased such that the target's tracking loops will follow the spoof signal instead of the real signals. Finally, the spoof signal is slewed in either space or time to drive the target's position or time estimate to where the attacker wants it to be.

There are a few anti-spoofing defenses available right now, but they are either expensive or ineffective. If the target has a high-quality inertial navigation system or clocks, then the slew rate available to the attacker is greatly reduced. There are also some defenses related to DGPS, but they require a separate base station and communication side-channel to execute.

Right now, the hardware cost to deploy an advanced attack like that is relatively cheap, and subject to Moore's Law. A GNU Radio USRP could do it right now, for example. The hardware cost to defend against it is expensive, and not getting any better. Changing the signal structure to incorporate cryptographically strong authentication is the only solution I can see to swing the pendulum back the other way.

It mentions protecting against jamming, but I hope they also explicitly make efforts against spoofing. I think that's the bigger security concern when your receiver thinks it has the right position, but an attacker is providing the signals and rerouting at their desire. Currently only tightly controlled military receivers have anti spoofing security distributed via the P(Y) code.

How would this work while still retaining the ability to have e.g. indoor GPS repeaters?[1].

1. http://www.gps-repeaters.com

It's a tricky problem. I could see enterprise solutions for private GPS networks that have signed messages similar to an asymmetric JWT signature. That way the message can be passed around and the client can assert if the message has been tampered with.

That approach requires the satellite networks to have knowledge of the key pairs for each client. Not something you'd see the government provide, but a possibility for commercial applications.

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