GSM Sniffing On A Budget With Multi-RTL

January 30, 2017 by Elliot Williams 26 Comments

If you want to eavesdrop on GSM phone conversations or data, it pays to have deep pockets, because you’re going to need to listen to a wide frequency range. Or, you can just use two cheap RTL-SDR units and some clever syncing software. [Piotr Krysik] presented his work on budget GSM hacking at Camp++ in August 2016, and the video of the presentation just came online now (embedded below). The punchline is a method of listening to both the uplink and downlink channels for a pittance.

[Piotr] knows his GSM phone tech, studying it by day and hacking on a GnuRadio GSM decoder by night. His presentation bears this out, and is a great overview of GSM hacking from 2007 to the present. The impetus for Multi-RTL comes out of this work as well. Although it was possible to hack into a cheap phone or use a single RTL-SDR to receive GSM signals, eavesdropping on both the uplink and downlink channels was still out of reach, because it required more bandwidth than the cheap RTL-SDR had. More like the bandwidth of two cheap RTL-SDR modules.

Getting two RTL-SDR modules to operate in phase is as easy as desoldering a crystal from one and slaving it to the other. Aligning the two absolutely in time required a very sweet hack. It turns out that the absolute timing is retained after a frequency switch, so both RTL-SDRs switch to the same channel, lock together on a single signal, and then switch back off, one to the uplink frequency and the other to the downlink. Multi-RTL is a GnuRadio source that takes care of this for you. Bam! Hundreds or thousands of dollar’s worth of gear replaced by commodity hardware you can buy anywhere for less than a fancy dinner. That’s a great hack, and a great presentation.
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Hacking Together A Serial Backpack

January 30, 2017 by Elliot Williams 30 Comments

A serial backpack is really nothing more than a screen and some microcontroller glue to drive it. And a hammer is nothing more than a hardened weight on the end of a stick. But when you’re presented with a nail, or a device that outputs serial diagnostic data, there’s nothing like having the right tool on hand.

[ogdento] built his own serial backpack using parts on hand and a port of some great old code. Cutting up a Nokia 1100 graphic display and pulling a PIC out of the parts drawer got him the hardware that he needed, and he found a good start for his code in [Peter Andersen]’s plain-old character LCD library, combined with a Nokia 1100 graphic LCD library by [spiralbrain]. [ogdento] added control for the backlight, mashed the two softwares together, and voilà!

A simple screen with a serial port is a great device to have on hand, and it makes a great project. We’ve seen them around here before, of course. And while you could just order one online, why not make your own? Who knows what kind of crazy customizations you might dream up along the way.

SDR And Node.js Remote-Controlled Monster Drift

January 30, 2017 by Elliot Williams 9 Comments

Most old-school remote controlled cars broadcast their controls on 27 MHz. Some software-defined radio (SDR) units will go that low. The rest, as we hardware folks like to say, is a simple matter of coding.

So kudos to [watson] for actually doing the coding. His monster drift project starts with the basics — sine and cosine waves of the right frequency — and combines them in just the right durations to spit out to an SDR, in this case a HackRF. Watch the smile on his face as he hits the enter key and the car pulls off an epic office-table 180 (video embedded below).

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Retrotechtacular: The Best Pendulum Clock

January 30, 2017 by Elliot Williams 31 Comments

Would you believe a pendulum clock that can keep time accurately to within one second per year? If you answered “yes”, you’ve either never tried to regulate a pendulum clock yourself, or you already know about the Shortt Clock. Getting an electromechanical device to behave so well, ticking accurately to within 0.03 parts per million, is no mean feat, and the Shortt clock was the first timekeeping device that actually behaves more regularly than the Earth itself. Continue reading “Retrotechtacular: The Best Pendulum Clock” →

Annoy Your Neighbors With MIDI Musical Siren

January 29, 2017 by Elliot Williams 33 Comments

[Yannick], aka [Gigawipf] brings us this (mostly) musical delicacy: a 3D-printed siren that’s driven by a brushless quadcopter motor, and capable of playing (mostly) any music that you’ve got the MIDI score for. This is a fantastic quickie project for any of you out there with a busted quad, or even some spare parts, and a 3D printer. Despite the apparent level of difficulty, this would actually be a great quickie weekend build.

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Japanese ISS Supply Ship Dual-Purposed As Tether Experiment

January 27, 2017 by Elliot Williams 35 Comments

When a rocket sends a capsule up with supplies for the International Space Station, they usually send a bunch of their trash back down with it, all of which burns up in the atmosphere on re-entry. But as long as you’ve got that (doomed) vehicle up there, you might as well do some science with it along the way. And that’s exactly what the Japanese Space Agency (JAXA) is doing with their Kounotori 6 supply ship that just left the ISS on Friday.

The experiment is with an electromagnetic tether that can be used to either turn electrical energy into kinetic or vice-versa. When you string a long conducting wire outwards from earth, the two ends pass through the earth’s magnetic field at different altitudes and thus pass through magnetic fields with different strengths, and an electrical potential is generated. In the KITE experiment (translated), a resistive load and an electron emitter on the supply ship are designed to burn up this electrical energy, lowering the ship’s kinetic energy, and dropping its orbit down to earth.
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Forth: The Hacker’s Language

January 27, 2017 by Elliot Williams 240 Comments

Let’s start right off with a controversial claim: Forth is the hacker’s programming language. Coding in Forth is a little bit like writing assembly language, interactively, for a strange CPU architecture that doesn’t exist. Forth is a virtual machine, an interpreted command-line, and a compiler all in one. And all of this is simple enough that it’s easily capable of running in a few kilobytes of memory. When your Forth code is right, it reads just like a natural-language sentence but getting there involves a bit of puzzle solving.

robot_forth_had-colors — From Thinking FORTH (PDF)

Forth is what you’d get if Python slept with Assembly Language: interactive, expressive, and without syntactical baggage, but still very close to the metal. Is it a high-level language or a low-level language? Yes! Or rather, it’s the shortest path from one to the other. You can, and must, peek and poke directly into memory in Forth, but you can also build up a body of higher-level code fast enough that you won’t mind. In my opinion, this combination of live coding and proximity to the hardware makes Forth great for exploring new microcontrollers or working them into your projects. It’s a fun language to write a hardware abstraction layer in. Continue reading “Forth: The Hacker’s Language” →