[HN Gopher] I discovered mysterious hidden signals on a public r...
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I discovered mysterious hidden signals on a public radio channel
(2013) [video]
Author : joebig
Score : 247 points
Date : 2024-10-27 00:09 UTC (22 hours ago)
(HTM) web link (media.ccc.de)
(TXT) w3m dump (media.ccc.de)
| quink wrote:
| (2013)
| dang wrote:
| Added above. Thanks!
| jfdi wrote:
| We need a tl;dr on this one!
| alwa wrote:
| At a very quick skim, seems she detected and decoded the RDS
| signal in the 57kHz subcarrier of an FM broadcast.
|
| https://www.mediarealm.com.au/articles/fm-rds-radio-data-sys...
| anthonyeden wrote:
| That Media Realm site is mine. Thanks for linking! RDS is one
| of those technologies that's been around for decades and
| still amazes people. You can buy hardware encoders for about
| AU$500 these days, and I love introducing stations to it and
| getting their name and song data to show up on car radios.
| melenaboija wrote:
| This is the blog post[1] from the presenter explaining part of
| it, with this request in the messages lol:
|
| - Sad to request, but can you take thisoffline. It is kind of
| our service you hacked :)
|
| [1]https://www.windytan.com/2013/05/a-determined-hacker-
| decrypt...
| alwa wrote:
| Thank you for that! I didn't have the patience for the video,
| but I found her pen-and-paper decryption in that blog post
| absolutely lovely.
| lelandfe wrote:
| That "take this post down on the first appearance of any
| complaint from any party" tact sure changed in a hurry, huh
| TechDebtDevin wrote:
| 1.75x, I can't watch any video at any other speed at this
| point.
| squarefoot wrote:
| Ever tried with Louis Rossmanns or Network Chuck videos? I
| can't watch them at more than 0.75.
| amatecha wrote:
| The actual title of the page is "My journey into FM-RDS" which
| definitely gives a better summary than what the current HN title
| says.
| dang wrote:
| I had switched it to that, but then noticed that joebig had
| used the subtitle, which is also legit.
| lostemptations5 wrote:
| I would have never read your title. The whole reason I clicked
| was because of the mystery element.
| jonex wrote:
| To me it sounded like click bait. So I checked comments and
| concluded that it was indeed about the very visible RDS
| signal and not some hidden channel used by some secretive
| agency that would indeed be somewhat mysterious.
|
| I don't think the fact that it worked in generating clicks is
| really an argument for bait titles. Given the positive
| comments about the content I think some editorializing could
| have been helpful to focus on the hacking journey aspect
| though, which seems to be the point rather the specifics of
| RDS itself.
| CyberDildonics wrote:
| Why do you need to be manipulated into reading something?
| When it turns out they are calling standard radio data
| "mysterious" don't you feel lied to?
| pessimizer wrote:
| Isn't that the definition of clickbait?
| ddtaylor wrote:
| I love the CCC website and the fact they host their own videos
| for a lot of reasons, but for some folks here is the YouTube
| video link:
|
| https://www.youtube.com/watch?v=CnnbFWTNxZI
| kchr wrote:
| They seem happy to host media for other conferences as well! <3
| Aachen wrote:
| For what folks would that be, then? Genuinely wondering why
| you'd want to click the big tech instead of self hosted link
| instead
| runj__ wrote:
| Someone wanting to subscribe to the YT-channel? I don't visit
| 500+ blogs per day just to check if there's something new. I
| do miss Google Reader, I think about it almost every single
| day, I tried using other tools but I really think the RSS-era
| is over.
| musictubes wrote:
| Maybe I'm doing it wrong but RSS works just fine most of
| the time for me. I use NewsBlur and does everything I need
| and more. What did reader have that no other RSS service
| doesn't?
| ddtaylor wrote:
| There was an alternate timeline where RSS went on to
| prosper. Instead it turned out like OpenID - a standard
| most aren't really using and it's all just SSO instead.
| immibis wrote:
| If you're on a smartphone, the Youtube app probably works
| better than whatever browser you're using. On the flip side,
| it probably has ads.
| matthberg wrote:
| I found on her website [1] that she released a RDS decoder tool
| [2] relatively recently (compared to the 2013 of the video at
| least). Looks like it works with a USB RTL-SDR [3] receiver or a
| pre-recorded file in a number of formats.
|
| [1]: https://www.windytan.com
|
| [2]: https://github.com/windytan/redsea
|
| [3]: https://www.rtl-sdr.com/about-rtl-sdr
| alfiedotwtf wrote:
| "So I got to work"...
|
| I love that hacker mindset :)
| sriram_malhar wrote:
| This was a such a refreshing talk. She was monitoring the FM
| channel using a spectrum analyser (as one does, of course, haha)
| and got curious about this strange signal showing up next to the
| FM radio Channel.
|
| The talk is about her attempts to learn about the Radio RDS
| (Radio Data System) standard, using a sound card to decode
| signals, finding a bit of bus-related information in that stream
| is weakly encrypted and proceeding to chasing it down. Very
| entertaining.
|
| I'm so glad such people exist. I wish I could be one of these
| fearless and supremely knowledgeable people!
| stavros wrote:
| > I wish I could be one of these fearless and supremely
| knowledgeable people!
|
| There's no trick to it (or there's a massive trick to it), you
| just refuse to let a mystery go until you know what's
| happening, mostly because figuring things out is fun.
|
| In the process, you gain a large amount of knowledge.
| smetj wrote:
| It comes down to genuine, natural unforced interest (its
| there or not) and mastering the ability to systematically
| deal with and how to tackle the next unknown. After years
| this make you a true wizard.
| deskr wrote:
| > mostly because figuring things out is fun
|
| I also think that figuring things out is one of life's most
| rewarding experiences.
|
| But I've found out a lot of people don't think like that.
| I've often been asked "but why are you doing this" on the
| topic of my "eccentric" projects. People often can't
| understand why I find it fascinating because they would only
| find it tormenting.
| amelius wrote:
| What if the data is encrypted? Do you keep on trying in a
| brute-force way?
| stavros wrote:
| You do whatever you think is fun, what do you mean?
| xattt wrote:
| I'm curious how folks who have the know-how to dissect a
| phenomenon "miss the forest for the trees" when they stumble upon
| a "mysterious" signal.
|
| Alternate data streams in FM like RDS, IBOC audio and FM time are
| not some new-fangled tech. This would/should be the first place
| to go to if you saw a signal that's not modulated to analog
| audio.
|
| Of course, the whole mystery aspect is just a hook and helps move
| the story along.
| therein wrote:
| Yeah more realistically it was like:
|
| > I was looking at FM radio channels on SDR (rtlsdr came out in
| 2010) and noticed the RDS. So I looked into it.
| sriram_malhar wrote:
| Oona (the author) knew about the existence of such things; it
| wasn't a mystery. The only reason it was strange is that
| because her radio had been knocked about during a move, it was
| strangely down-shifting the data channel ... she was not
| monitoring the FM (from what I could make out), but the actual
| audio from the radio.
|
| This was just ('just' for her, impressive for me) an exercise
| of going down the rabbit hole, and then curating that tour for
| us.
| ezcrypt wrote:
| Rather, I don't think the data channel was actually down-
| shifted, but that it wasn't filtered out (probably due to a
| broken analog filtering circuit after the fall), so it was
| still outside of the audible spectrum but available to the
| sound card and hence visible in her software spectrum
| analyzer. It also sounded like she was seeing some aliasing
| effect, i.e. that the data signal was probably out of band
| for the sound card ADC, but "folded" down into the sampler
| frequency range due to Nyquist folding "magic" (which is
| maybe what you meant with "down-shifting", now that I think
| about it?).
| sriram_malhar wrote:
| She does speak of aliasing.
| 0898 wrote:
| One thing I often wonder about with RDS: How do they stop the
| traffic alert ("TA") feature being abused by stations to grab
| listeners?
| looperhacks wrote:
| I think nobody has to prevent abuse because listeners will
| either turn off traffic alerts or switch to a different
| channel.
|
| Besides that, FM broadcasting isn't a lawless place and is
| regulated by the government. Abuse will most likely lead to
| some kind of penalty, but I can't be bothered to read through
| the laws to confirm it :P
| fhars wrote:
| The same way the prevent stations from broadcasting 90 seconds
| or more of pure silence: you loose your license if you do.
| GranPC wrote:
| > broadcasting 90 seconds or more of pure silence
|
| Have a link or info on this? Sounds interesting but can't
| find anything.
| fhars wrote:
| It is a rule in Germany, I know about it because we did
| some distributed cooperation stuff with community radio
| stations and some hacking events during the pandemic, and
| making sure that no matter what happens with the network
| between the speakers, the coordinating host, and server of
| the radio station, we never send out silence, was quite an
| important concern. I can't quote you the exact line of the
| law,though.
| GJim wrote:
| They don't.
|
| Back in the day, it wasn't uncommon for pirate radio stations
| to drum up listeners by using TA to advertise short snippets.
| teeray wrote:
| The almighty FCC fine is the deterrent
| ARob109 wrote:
| Not sure about TA, but definitely saw radio station in
| Indianapolis using RDS to broadcast advertisements. In between
| the artist/song info, ads for an injury lawyer appeared.
| Thought it was super lame use of RDS.
| stavros wrote:
| This was great, I love these rabbit holes people go down, and
| it's great when they then share the results. Very fun watch.
| user3939382 wrote:
| I was picking up WCBS in NYC at 5.105 GHz, near the antenna at
| Empire State. Never could figure it out, their engineers didn't
| know why either.
| wildzzz wrote:
| It was probably getting picked up by some component in a
| microwave transmitter and getting mixed into the signal.
| yarg wrote:
| This makes me wonder, how do you reliably and securely encode
| steganographic content for distribution within a noisy medium?
| ezcrypt wrote:
| In this case I think it's mostly about using different sub-
| carriers (kind of a "channel in the channel"), so that the data
| information and the audio are separated in frequency and do not
| disturb each other. That's generally called Frequency Division
| Multiple Access (FDMA), IIRC.
|
| Another more advanced technique is Code Division Multiple
| Access (CDMA), e.g. used by GPS and some mobile communication
| modulation schemes. It allows you to have multiple senders on a
| single radio carrier frequency, and the receiver "selects"
| which sender to listen to by knowing its "code".
|
| There's also Time Division Multiple Access (TDMA), i.e. senders
| take turns sending content in allocated time slots.
| Aachen wrote:
| Wow, was that 2013? I saw this talk irl, can't believe it has
| been that long
| Zigurd wrote:
| Are there still apps and the underlying hardware in smartphones
| to receive and decode FM RDS? IIRC some phone chips had FM radio
| receivers, but there were limitations like needing a wired
| headphone plugged in so that the headphone cable could be used as
| an antenna. I know a USB SDR could do it, but it would be neat if
| this were still a latent capability in the phone.
|
| Of course I did a search in the Play Store but it's crowded with
| streaming radio apps and SDR apps.
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(page generated 2024-10-27 23:01 UTC)