The Quiet Numbers Station: Decoding Nineteen Years of GPS Cryptography

https://www.benthamsgaze.org/2026/06/02/the-quiet-numbers-station-decoding-nineteen-years-of-gps-cryptography/

by lordgilman • 2 months ago

133 84 2 months ago

benthamsgaze.org

https://lsc-pagepro.mydigitalpublication.com/publication/?i=...

PDF: https://cdn.coverstand.com/61061/865273/2c88ea662e2b57478723... (article is on page 62)

transistor-man• 2 months ago

This is a fantastic writeup

timeinput2• 2 months ago

This is an interesting article. It has a very strong AI accent.

I really wish I could tell how real it is. When some part of it I can tell is AI slop, how much of it is AI slop? Inside GNSS has always been a marketing rag with sometimes some interesting articles.

The author is a security researcher, so maybe poking at GPS bits makes sense, but talking about floating point bit depth? There's too much slop for me to figure out if there's anything of real interest or if this is just a hallucination.

Edit. After reading more carefully this is 100% AI slop. Inside GNSS published Steven Murdoch's chat gpt session. Maybe some data was transmitted? The only way you'll actually know is to redo the research your self. There are many fabrications / confabulations that clearly happen with AI in the text.

rcxdude2• 2 months ago

I've worked with the guy credited in the article before, so I'll vouch for his general credibility and the underlying information likely being solid: there's good evidence for this field being some kind of encrypted data stream, probably key distribution, and the behaviour has changed over time. But the breathless LLM-tone really did make it hard to read.

timeinput2• 2 months ago

Cool. Some data may have been transmitted over GPS. That's interesting and note worthy.

If only that was all that was posted.

Instead there's this stuff that makes me question Steven Murdoch's research practices. If you're willing to publish slop are his research practices slop? Can I trust any paper he creates in the future when I can tell this one has factual errors? Why should I bother reading it?

I actually think he's a good researcher from a little reading. I wish he hadn't done this.

ekelsen• 2 months ago

So much AI. I stopped immediately. He might have something interesting to say, but apparently not important enough for him to write about it himself, so not important enough for me to read it either.

sjm2173• 2 months ago

The code is all available and every claim is traceable back to the statistical analysis. Results are reproducible from the original data which is archived on Zenodo. Further analysis would be very welcome. https://github.com/sjmurdoch/gps-special-messages

dang6• 2 months ago

(This comment was posted when the article was https://lsc-pagepro.mydigitalpublication.com/publication/?i=...; we've since done a merge and changed the URL above)

applicative2• 2 months ago

Paradoxically, in the blog post he speaks with his own voice, describing the evidence better amassed in ... the AI written article.

7777777phil• 2 months ago

Slightly related the latest Veritasium Video: Something is jamming GPS over Europe.

https://youtu.be/tz23G_UXCGA

newtwentysix• 2 months ago

spwa4• 2 months ago

TLDW: Russia is jamming GPS and GNSS over Europe, purposefully, using a constellation of military satellites.

Theory is that Russia is constantly practicing to totally disrupt GPS and GNSS (and the Chinese system) across all of Europe.

floxy• 2 months ago

Anyone have a good source to read up on the current state of the art for daytime celestial navigation? Maybe there isn't too much in the public domain, because things like GPS work so well. But I'd guess that since you can't easily artificially jam celestial navigation there would be military research on this. But I suppose clouds also limit the practicality as well.

https://www.scientificamerican.com/article/how-to-see-stars-...

dabluecaboose• 2 months ago

GNSS is just the catch-all term. It stands for "Global Navigation Satellite System".

The Chinese system is called BeiDou.[1]

[1] https://en.wikipedia.org/wiki/Satellite_navigation#BeiDou_(2...

zerobees• 2 months ago

"Numbers station" is a weird analogy, because the idea of a numbers station was to broadcast messages to undercover operatives in a way that can be received using unmodified (and therefore non-suspicious) household radio receivers.

Here, it appears to be a rekeying system for specialized military gear.

tokai2• 2 months ago

Yeah its not a number station at all.

Analemma_• 2 months ago

I disagree? The point of a numbers station is that it broadcasts in the clear and anyone with a receiver can get it, but only people with the appropriate decryption key can make any use of it. Since it's broadcasting all the time, there's no need for steganography or covert transmission. That's exactly what a numbers station is.

Where the article loses me is the implication that this is somehow sinister or beyond the pale: it's just piggybacking on a global transmitter network that exists anyway, why not?

moritzwarhier4• 2 months ago

I think it's simply because of using a public channel for encrypted communication.

ronsor• 2 months ago

Technically all RF communications are "public." You have to use encryption if you want security.

866-RON-0-FEZ• 2 months ago

Yeah GPS is not the people's airwaves it is operated by the US Space Force, I suggest you read up on your history.

moritzwarhier4• 2 months ago

Thanks for all the replies: my phrasing was indeed bad I guess!

A "public channel" is a very broad definition, and most communication channels, including those used for encrypted communication, are by design more or less "public".

Situation with GPS that feels similar to "number stations" (which I only know about thanks to Boards of Canada's album "Geogaddi", tbh^^) is that encrypted messages are deliberatily broadcasted, not that the channel is in some way "public". The latter also applies to all encrypted internet traffic, I guess.

anigbrowl4• 2 months ago

“Every receiver in the world decodes Subframe 4, Page 17,” Murdoch said in his new article. [...] “Every GPS satellite is a numbers station,” he concluded.

matthewdgreen2• 2 months ago

You're assuming it requires specialized military gear, as opposed to consumer gear with a flashed firmware. I believe GPS L1 C/A subframe 4 is on the ordinary L1 C/A civil signal, which means commercial receivers can receive it. They just can't (ordinarily) decrypt it. But a few KB of extra code would change that. A pretty broad set of Android phones can receive this data, without even needing to reflash the GPS firmware: you can decrypt on the application processor, since this field is readable.

WarOnPrivacy2• 2 months ago

You're assuming it requires specialized military gear, as opposed to consumer gear with a flashed firmware.

The author studied this supposition [code intended for mil gear] for some time and learned this.

    On 26 May 2011, all 31 active GPS satellites switched to the
    0xAA placeholder within just a few hours.
    This rapid daily change perfectly matches the operational
    rollout of the U.S. Over-the-Air Distribution (OTAD) network.

Angostura• 2 months ago

So, a number station sending a message 'detonate the bomb' isn't a number station, because most people don't have the bomb?

moritzwarhier4• 2 months ago

Later submission:

https://news.ycombinator.com/item?id=48414479

https://www.404media.co/the-u-s-military-quietly-turned-gps-...

The 404 article seems fluff-free and cites

https://insidegnss.com/current-issue/

as source.

dang6• 2 months ago

We'll merge the threads and put the relevant links in the toptext. Thanks!

josefritzishere• 2 months ago

best zero day exploit ever

gruez• 2 months ago

That's not what a 0day exploit is. It doesn't allow you to take over arbitrary GPS receivers, for instance.

eagerpace2• 2 months ago

GPS was always a dual use system. This is very detailed and specific, but not interesting or surprising. Research has been study GPS signal data, found parts that are encrypted and he doesn’t understand. The end. Article seems only intended to generate an emotional response of “how dare they use GPS for war, man!”

sgjohnson2• 2 months ago

GPS was always a dual use system

It wasn't. It was going to be a military-only system, until KAL007 presented the obvious life-saving civilian case.

But yes, the title of this article might as well read "Satellite system developed for military use is being used for a military purpose."

eagerpace2• 2 months ago

Even better, thanks for clarifying. It’s that kind of omission from the article that makes the rest of it hard to swallow. Even if it is technically correct. Which is sadly the case for most “journalism” these days.

golem14• 2 months ago

It’s not surprising, but I find it interesting.

jp42• 2 months ago

Meanwhile Starlink and Starshield: Hold my beer ;-)

rafram• 2 months ago

Clickbait from 404 Media? Surely not!

The part they kept out of the headline:

for use in distributing the keys for accessing the military GPS signals

It’s common knowledge that the military has access to a separate, encrypted, higher-precision GPS signal. “Numbers station” implies that they’re distributing unrelated encrypted information, but they’re not; it’s not surprising that GPS signals would be used to deliver information related to GPS, even if only military receivers have any use for it!

stackghost• 2 months ago

It’s common knowledge that the military has access to a separate, encrypted, higher-precision GPS signal.

The most militarily-valuable aspect of the military GPS signals is actually the anti-spoofing qualities, rather than the higher precision. Survey-grade GPS gear has been able to achieve centimetre-level precision from the regular civilian signals for several years now, using RF fuckery like tracking the phase angle and other techniques.

To be sure, you want the precision too. NATO countries have M982 Excalibur GPS-guided artillery rounds that are precise enough that you can select not just the building you want to hit but the specific window you want the round to enter.

But the primary benefit of the encrypted signal is that it provides cryptographic assurance that the signal is not spoofed and one can be confident that one's GPS-guided cruise missile or other munition is not being diverted off-course.

Nowadays the military GPS signal has moved from transmitting the legacy "P(Y) code", which is a Cold War-era design, to the "M code" which incorporates several decades' worth of lessons learned in terms of spoofing resistance, cryptographic authentication, etc. It's actually a really neat rabbit hole to climb down.

causal• 2 months ago

I don't think this qualifies as clickbait in the sense that the headline mismatches the contents. My experience with 404 Media is that they treat every article like they've just released the Pentagon Papers, so you just have to read with that in mind.

SllX3• 2 months ago

My experience with 404 Media is that they treat every article like they've just released the Pentagon Papers

I think you’ve perfectly phrased exactly what it is that annoys me when I see a 404 Media headline. When it was a new shop, I stomached it more, but this is every single headline I ever see from them.

05• 2 months ago

has access to a separate, encrypted, higher-precision GPS signal.

That's not it, though. This is available on the consumer L1 band, and you can even read that info using a $5 Ublox receiver (UBX-RXM-SFRBX command).

kotaKat• 2 months ago

Yeah, but the DAGRs out there hop around on both sets. You can run a DAGR without keys and it'll use civ GPS just fine. It'd make sense to have the hidden OTAR/OTAP running on a hidden chunk of L1 traffic.

https://www.baesystems.com/en/product/defense-advanced-gps-r...

dang6• 2 months ago

(This comment was originally posted to https://news.ycombinator.com/item?id=48414479, where the article was https://www.404media.co/the-u-s-military-quietly-turned-gps-.... We've since merged the threads.)

ck2• 2 months ago

People are complaining about a clickbaity title but it's a fascinating article I am not sure most would read otherwise

What's interesting to me is how out of date US GPS system is compared to China's BeiDou

and while most US GPS receivers will use Russia's GLONOSS, China's BeiDou is blocked

https://news.ycombinator.com/item?id=47849174

anigbrowl4• 2 months ago

Indeed. i have some GPS receiver modules and had wondered about this data, I had assumed it was imprecision in my device or something to do with a satellite moving around. I'll have to plug it in and go back for another look.

applicative2• 2 months ago

The going wisdom seems to be that the EU's Galileo is the most accurate system for civilian use. GPS has undergone frequent systematic update for almost a half century.

dang6• 2 months ago

(This comment was originally posted to https://news.ycombinator.com/item?id=48414479 - we've since merged the threads)

kortilla• 2 months ago

What's interesting to me is how out of date US GPS system is compared to China's BeiDou

It’s significantly older though. What would you expect?

entrope2• 2 months ago

Two things amaze me about GPS. First, that there are still four Block IIR and seven Block IIR-M satellites operational; these had 7.5 year design lives and were launched by 2004 and 2009 respectively. Second, that L1C, L5 and L2C are all still pre-operational thanks to the OCX debacle. L1C and L2C really modernize the signal structure to improve accuracy.

NelsonMinar• 2 months ago

Summary from the study author: https://www.benthamsgaze.org/2026/06/02/the-quiet-numbers-st...

PDF of article (page 62) https://cdn.coverstand.com/61061/865273/2c88ea662e2b57478723...

dang6• 2 months ago

Thank you! That first link does seem to be the best one (in terms of easiness to access and information explained). We'll use it above.

anigbrowl4• 2 months ago

The story links to the current issue of the Inside GNSS magazine but the article isn't available in the digital edition, apparently. It's in the print edition, readable at https://lsc-pagepro.mydigitalpublication.com/publication/?i=...

The source data and analytical code (in Julia) is also available at https://lsc-pagepro.mydigitalpublication.com/publication/?i=...

In my view people nitpicking the 404 media story are being ridiculous. Everyone in their audience knows GPS originated as a military system, indeed I think most of teh general public knows that. Bashing them for not mentioning this is just looking for something to be mad about.

Lammy• 2 months ago

May 26, 2011
No publicly recorded NANU announces a fleet-wide event of this kind in the surrounding window.

I do remember living through this one in February 2011 which was very strange at the time: https://web.archive.org/web/20111015232120/http://navcen.usc...

“SOUTHEAST ATLANTIC COAST: GPS Testing Information THE GPS NAVIGATION SIGNALS MAY BE UNRELIABLE FROM 20 JAN 2011 - 22 FEB 2011 FROM 0000Z - 0245Z DUE TO TESTING ON GPS FREQUENCIES USED IN SHIPBOARD NAVIGATION AND HANDHELD SYSTEMS. GPS SYSTEMS THAT RELY ON GPS, SUCH AS E-911, AIS AND DSC, MAY BE AFFECTED WITHIN A 150 NM RADIUS OF POSITION 30 49.09N 80 28.18W. DURING THIS PERIOD GPS USERS ARE ENCOURAGED TO REPORT ANY GPS SERVICE OUTAGES THAT THEY MAY EXPERIENCE DURING THIS TESTING VIA THE NAVIGATION INFORMATION SERVICE (NIS) BY CALLING (703) 313-5900 OR BY USING THE NAVCEN WEB SITE'S GPS REPORT A PROBLEM WORKSHEET AT WWW.NAVCEN.USCG.GOV.”

I specifically remember it because I was trying to navigate to the Atlanta IKEA but my phone showed me as being, like, south of Macon; ~100mi of error. That timeframe could fit if they were testing something like key availability in a spoofing scenario before enabling real key material transmission.

dang6• 2 months ago

skeledrew• 2 months ago

[in a new article in Inside GNSS](https://insidegnss.com/current-issue/?ref=404media.co)

These people need to mind their links. Unless that "current-issue" is the only/last one.

buredoranna• 2 months ago

Since we're talking numbers stations...

I'll take this opportunity to plug the CONET project: Recordings of Shortwave Numbers Stations

https://en.wikipedia.org/wiki/The_Conet_Project

https://archive.org/details/The-Conet-Project

[edit: formatting]

zuzululu• 2 months ago

I know it isn't really a number station but I wanted it to be true...

Someone broadcasting one time pad messages using GPS over years...

a spy operative using jogging app changing routes slightly

or maybe a cartel member embedded inside highly hostile countries like Singapore

somat• 2 months ago

An interesting lesser known role of GPS is that it is part of the US nuclear monitoring network and it's L3 signal is part of this.

https://www.youtube.com/watch?v=DjLnIb41DuQ I Found The US Nuclear Detection System In Space (saveitforparts)

thenthenthen• 2 months ago

So similar to the constellation discussed in the GNSS jamming article here? > https://news.ycombinator.com/item?id=48409664

opengrass• 2 months ago

Messages would be split over multiple mediums or be slow.

masfuerte• 2 months ago

To make processing this massive dataset practical, we built a Julia pipeline to extract the bits directly into a DuckDB database.

The raw data is a bit more than 1GB per annum.

The data of interest is 176 bits every 12.5 minutes for 19 years. That is, about 17MB of data. Possibly multiplied by the number of satellites, roughly thirty.

It's not big data.

sjm2173• 2 months ago

The dataset was 136GB (about 7GB per annum), and the Python implementation took 45 hours for each run. The Julia code that processed the whole dataset and built the database took 5 hours, which made iterative development much more pleasant. Of course, later stages in the pipeline had much less data to process and so were much faster. With metadata and indices, that was about 3GB. It's bigger than your estimate since there are multiple observations of the same satellite.

sjm2173• 2 months ago

Though I take your point that it’s not big data by the conventional use (i.e. requiring a distributed computing to process). The phrasing in the original article was better: “To make iterative analysis practical, we wrote a Julia pipeline: NetCDF source files are converted to Apache Arrow, then thread-parallel bit extraction is performed into a DuckDB database.”

The Quiet Numbers Station: Decoding Nineteen Years of GPS Cryptography

Related Stories