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Reverse Engineering a Mysterious UDP Stream in My Hotel (2016) (gkbrk.com)
266 points by SuperNinKenDo on Jan 21, 2018 | hide | past | web | favorite | 15 comments

What the hell? I can’t believe I spent time for this. It’s just elevator music. It is played in the hotel corridors around the elevators. Oh well, at least I can listen to it from my room now.

One would have thought the next step would have been to arrange for better (i.e. more metal) elevator music? If it's multicast, it would be surprising if there were a lot of authentication on the speaker side.

My thought exactly. Make voice recordings and randomly broadcast ghostly screams into the elevators. Not something I would do, but definitely a DEFCON prank waiting to happen.

"Attention customers, due to signal delays, this elevator is now running on the express line. For local service, please transfer to the 1 train at the 168th street station."

``Hello,'' said the elevator sweetly, ``I am to be your elevator for this trip to the floor of your choice. I have been designed by the Sirius Cybernetics Corporation to take you, the visitor to the Hitch Hiker's Guide to the Galaxy, into these their offices. If you enjoy your ride, which will be swift and pleasurable, then you may care to experience some of the other elevators which have recently been installed in the offices of the Galactic tax department, Boobiloo Baby Foods and the Sirian State Mental Hospital, where many ex-Sirius Cybernetics Corporation executives will be delighted to welcome your visits, sympathy, and happy tales of the outside world.''

``Yeah,'' said Zaphod, stepping into it, ``what else do you do besides talk?''

``I go up,'' said the elevator, ``or down.''

``Good,'' said Zaphod, ``We're going up.''

``Or down,'' the elevator reminded him.

``Yeah, OK, up please.''

There was a moment of silence.

``Down's very nice,'' suggested the elevator hopefully.

``Oh yeah?''


``Good,'' said Zaphod, ``Now will you take us up?''

``May I ask you,'' inquired the elevator in its sweetest, most reasonable voice, ``if you've considered all the possibilities that down might offer you?''

Is there a reason you're using those god-awful ticks instead of normal quotation marks?

I guess you're supposed to render it as LaTeX in your head.

The reason is that I copy-pasted the excerpt from an Angelfire website that wrote them using those...

s/Not something I would do/Not something I would admit to doing on a public forum/

Fixed that for you ;)

Then program a Raspberry Pi to generate this but only between midnight at 2AM and hide it behind a wall socket.

Haha, the best part was the multiple comments complaining about outdated magic files seeing Nintendo everywhere.

One wonders if selecting "decode as RTP" in Wirehshark might've saved some time figuring out the header situation. Though I thought that was 12 bytes, not 8, offhand.

This same guy written has a lolcat in 64 bit assembly. https://gkbrk.com/2016/07/lolcat-clone-in-x64-assembly/

In the few times I've tried to follow a completely unknown protocol, I've often failed to make the kind of leaps that this person was able to. To that end, I often get stuck and unable to make progress. I really want to learn to reverse engineer, but I feel like I don't innately know enough of the patterns.

In the same vein, I often missed the patterns required to solve difficult integration and derivatives in calculus. I believe I need more practice in that regard. Anyone have recommendations for simple protocol reverse engineering practice?

I love stories like these.

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