The 90s were a wonderful time for portable communications devices. Cell phones had mass, real buttons, and thick batteries – everything you want in next year’s flagship phone. Unfortunately, Zach Morris’ phone hasn’t been able to find a tower for the last decade, but that doesn’t mean these phones are dead. This weekend at Shmoocon, [Brandon Creighton] brought these phones back to life. The Motorola DynaTAC lives again.
[Brandon] has a history of building ad-hoc cell phone networks. A few years ago, he was part of Ninja Tel, the group that set up their own cell phone network at DEF CON. That was a GSM network, and brickphones are so much cooler, so for the last few months he’s set his sights on building out a 1G network. All the code is up on GitHub, and the hardware requirements for building a 1G tower are pretty light; you can roll your own 1G network for about $400.
The first step in building a 1G network, properly referred to as an AMPS network, is simply reading the documentation. The entire spec is only 136 pages, it’s simple enough for a single person to wrap their head around, and the concept of a ‘call’ really doesn’t exist. AMPS looks more like a trunking system, and the voice channels are just FM. All of this info was translated into GNU Radio blocks, and [Brandon] could place a call to an old Motorola flip phone.
As far as hardware is concerned, AMPS is pretty lightweight when compared to the capabilities of modern SDR hardware. The live demo setup used an Ettus Research USRP N210, but this is overkill. These phones operate around 824-849 MHz with minimal bandwidth, so a base station could easily be assembled from a single HackRF and an RTL-SDR dongle.
Yes, the phones are old, but there is one great bonus concerning AMPS. Nobody is really using these frequencies anymore in the US. That’s not to say building your own unlicensed 1G tower in the US is legally permissible, but if nobody reports you, you can probably get away with it.
Looking for all the world like something assembled from the Radio Shack parts department – remember when Radio Shack sold parts? – [Mr_Volt]’s build is a celebration of the look and feel of a hobbyist build from way back when. Looking a little like a homebrew DynaTAC 8000X, the brushed aluminum and 3D-printed ABS case sports an unusual front panel feature – a working rotary dial. Smaller than even the Trimline phone’s rotating finger stop dial and best operated with a stylus, the dial translates rotary action to DTMF tones for the Feather FONA board inside. Far from a one-trick pony, the phone sports memory dialing, SMS messaging, and even an FM receiver. But most impressive and mysterious is the dial mechanism, visible through a window in the wood-grain back. Did [Mr_Volt] fabricate those gears and the governor? We’d love to hear the backstory on that.
[Marcel] was trying to shoehorn a few new parts into his trusty Nexus 5 phone. If you’ve ever opened one of these little marvels up, you know that there’s not much room under the hood to work with. Pulling out some unnecessary parts (like the headphone jack) buys some space, but then how to wire it all up?
[Marcel] needed a multi-wire connector that’s as thin as possible, but he wasn’t going to go the order-Kapton-flex route. Oh no! He built one himself from masking tape and the strands from a stranded wire. Watch the video how-to if that alone isn’t enough instruction.
An IMSI catcher is an illicit mobile phone base station designed to intercept the traffic from nearby mobile phones by persuading them to connect to it rather than the real phone company tower. The IMSI in the name stands for International Mobile Subscriber Identity, a unique global identifier that all mobile phones have. IMSI catchers are typically used by government agencies to detect and track people at particular locations, and are thus the subject of some controversy.
As is so often the case when a piece of surveillance technology is used in a controversial manner there is a counter-effort against it. The IMSI catchers have spawned the subject of this post, an IMSI catcher detector app for Android. It’s a work-in-progress at the moment with code posted in its GitHub repository, but it is still an interesting look into this rather shadowy world.
How them you might ask, does this app hope to detect the fake base stations? In the first case, it will check the identity of the station it is connected to against a database of known cell towers. Then it will try to identify any unusual behaviour from the base station by analysing its traffic and signal strength. Finally it will endeavour to spot anomalies in the implementation of the cell phone protocols that might differentiate the fake from the real tower.
They have made some progress but stress that the app is in alpha stage at the moment, and needs a lot more work. They’re thus inviting Android developers to join the project. Still, working on projects is what the Hackaday Prize is all about.
Think not of what you see, but what it took to produce what you see
Randomness is all around you…or so you think. Consider the various shapes of the morning clouds, the jagged points of Colorado’s Rocky Mountains, the twists and turns of England’s coastline and the forks of a lightning bolt streaking through a dark, stormy sky. Such irregularity is commonplace throughout our natural world. One can also find similar irregular structures in biology. The branch-like structures in your lungs called Bronchi, for instance, fork out in irregular patterns that eerily mirror the way rivers bifurcate into smaller streams. It turns out that these irregular structures are not as irregular and random as one might think. They’re self-similar, meaning the overall structure remains the same as you zoom in or out.
The mathematics that describes these irregular shapes and patterns would not be fully understood until the 1970s with the advent of the computer. In 1982, a renegade mathematician by the name of Benoit Mandelbrot published a book entitled “The Fractal Geometry of Nature”. It was a revision of his previous work, “Fractals: Form, Chance and Dimension” which was published a few years before. Today, they are regarded as one of the ten most influential scientific essays of the 20th century.
Mandelbrot coined the term “Fractal,” which is derived from the Latin word fractus, which means irregular or broken. He called himself a “fractalist,” and often referred to his work as “the study of roughness.” In this article, we’re going to describe what fractals are and explore areas where fractals are used in modern technology, while saving the more technical aspects for a later article.
The idea is that phones are increasingly complex and potentially vulnerable to all kinds of digital surveillance. Even airplane mode is insufficient for knowing that your phone isn’t somehow transmitting information. The paper looks at the various radios on the iPhone, going so far as opening up the device and reading signals at each of the chips for cell, WiFi, Bluetooth, GPS, and NFC to determine whether the chip itself is doing anything, regardless of what the screen says. This introspection can then be used to be confident that the phone is not communicating when it shouldn’t be.
The paper goes on to propose a device that they will prototype in the coming year which uses an FPC that goes into the phone through the SIM card port. It would contain a battery, display, buttons, multiple SIM cards, and an FPGA to monitor the various buses and chips and report on activity.
Significant hacking of an iPhone will still be required, but the idea is to increase transparency and be certain that your device is only doing what you want it to.
The launch of Pokemon Go has unleashed the franchise upon the world once again but this time it’s encouraging users to get active and socialize in the great outdoors. To show off their dedication to the cause, [Npoole] 3D printed a Pokédex external battery and case to combat the game’s already legendary drain on their Galaxy S4’s resources.
Mimicking the first-generation Kanto design, [Npoole] 3D printed it in red ABS and added a small circuit with a red, yellow and green LED to complete the effect. Inside, a 18650 lithium cell provides the much-needed backup power via a micro B plug and is boosted to 5V with a LiPo charger/booster board. Despite a switch on the circuit, the battery slowly drains so that’s something to be corrected in a future version.
As you can see, there is still some room left over in the external bat–I mean–Pokédex, and [Npoole] intends to add another battery and a cooling fan to further improve the design. The result is a little bulky, but for new and diehard fans alike, a working Pokédex definitely worth it.