A lot of you use WiFi for your Internet of Things devices, but that pretty much rules out a battery-powered deployment because WiFi devices use a lot of juice. Until now. Researchers at the University of Washington have developed a passive WiFi implementation that uses only microwatts per device.
Working essentially like backscatter RFID tags do, each node has a WiFi antenna that can be switched to either reflect or absorb 2.4 GHz radiation. Your cell phone, or any other WiFi device, responds to this backscattered signal. All that’s missing is a nice steady signal to reflect.
A single, plugged-in unit provides this carrier wave for multiple WiFi sensor nodes. And here’s the very clever part of the research: to keep the carrier from overwhelming the tiny modulated signal that’s coming from the devices, the plugged-in unit transmits off the desired frequency and the battery-powered units modulate that at just the right difference frequency so that the resulting (mixed) frequency is in the desired WiFi band.
If you’re a radio freak, you’ll recognize the WiFi node’s action being just like a frequency mixer. That’s what the researchers (slightly mysteriously) refer to as the splitting of the analog transmission stage from the digital. The plugged-in unit transmits the carrier, and the low-power nodes do the mixing. It’s like a traditional radio transmitter, but distributed. Very cool.
There’s a bunch more details to making this system work with consumer WiFi, as you’d imagine. The powered stations are responsible for insuring that there’s no collision, for instance. All of these details are very nicely explained in this paper (PDF). If you’re interested in doing something similar, you absolutely need to give it a read. This idea will surely work at lower frequencies, and we’re trying to think of a reason to use this distributed transmitter idea for our own purposes.
And in case you think that all of this RFID stuff is “not a hack”, we’ll remind you that (near-field) RFID tags have been made with just an ATtiny or with discrete logic chips. The remotely-powered backscatter idea expands the universe of applications.
Thanks [Ivan] for the tip!
Continue reading “Passive WiFi On Microwatts”
There are two sides to every coin. Instead of swiping or using a chip reader with your credit card, some companies offer wireless cards that you hold up to a reader for just an instant. How convenient for you and for anyone who might what to read that data for their own use. The same goes for RFID enabled passports, and the now ubiquitous keycards used for door access at businesses and hotels. I’m sure you can opt-out of one of these credit cards, but Gerald in human resources isn’t going to issue you a metal key — you’re stuck hauling around that RFID card.
It is unlikely that someone surreptitiously reading your card will unlock your secrets. The contactless credit cards and the keylock cards are actually calculating a response based on a stored key pair. But you absolutely could be tracked by the unique IDs in your cards. Are you being logged when passing by an open reader? And other devices, like public transit cards, may have more information stored on them that could be harvested. It’s not entirely paranoid to want to silence these signals when you’re not using them.
One solution is to all of this is to protect your wallet from would-be RFID pirates. At this point all I’m sure everyone is thinking of a tin-foil card case. Sure, that might work unless the malicious reader is very powerful. But there’s a much more interesting way to protect against this: active RFID scrambling with a project called GuardBunny. It’s a card that you place next to whatever you want to protect. It’s not really RFID — I’ll get that in a moment — but is activated the same way and spews erroneous bits back at any card reader. Kristin Paget has been working on GuardBunny for several years now. As of late she’s had less time for active development, but is doing a great thing by letting version 1 out into the world for others to hack on. In her talk at Shmoocon 2016 she walked through the design, demonstrated its functionality, and shared some suggestions for further improvement.
Continue reading “GuardBunny Active RFID Protection Going Open Hardware”
If you’ve been to downtown San Francisco lately, you might have noticed something odd about the decorative trees in the city: they’re now growing fruit. This is thanks to a group of people called the Guerrilla Grafters who are covertly grafting fruit-bearing twigs to city tress which would otherwise be fruitless. Their goal is to create a delicious, free source of food for those living in urban environments.
Biology-related hacks aren’t something we see every day, but they’re out there. For those unfamiliar with grafting, it’s a process that involves taking the flowering, fruiting, or otherwise leafy section of one plant (a “scion”) and attaching them to the vascular structure of another plant that has an already-established root system (the “stock”). The Guerrilla Grafters are performing this process semi-covertly and haven’t had any run-ins with city officials yet, largely due to lack of funding on the city’s part to maintain the trees in the first place.
This hack doesn’t stop at the biological level, though. The Grafters have to keep detailed records of which trees the scions came from, when the grafts were done, and what characteristics the stock trees have. To keep track of everything they’ve started using RFID tags. This is an elegant solution that can be small and inconspicuous, and is a reliable way to keep track of all of one’s “inventory” of trees and grafts.
It’s great to see a grassroots movement like this take off, especially when it seems like city resources are stretched so thin that the trees may have been neglected anyway. Be sure to check out their site if you’re interested in trying a graft yourself. If you’re feeling really adventurous, you can take this process to the extreme.
Thanks to [gotno] for the tip!
The MakerBarn is a new makerspace between The Woodlands and Tomball, TX (north of Houston). [George Carlson], one of the founders and a retired design engineer, wanted to make sure only members certified on a machine could use it. He worked with [Kolja Windeler] to create the MACS or Makerspace Access Control System. He has one video explaining MACS and, after the break, another explaining the browser based user interface for the system.
A control box, [George] calls them stations, controls the power to a machine. Member badges have an RFID tag that is read when inserted into the station’s reader. If the member is authorized to use the machine, the power is enabled. For safety, the member’s badge must remain in the reader to maintain power. The reader uses a Photon board from Particle with a WiFi link to a Raspberry Pi server.
[Kolja] developed a Pi system to maintain a database of member numbers and the machines they can use. The list is sent to the stations periodically or when updates occur. The user interface is browser based on the MakerBarn’s LAN so it can be maintained by a computer or smartphone in the space. Presently 21 MACS modules have been built with some going to Hanover University in Germany for their auto hobby shop.
Not only did [George] lead the effort on creating MACS but has been key to getting the construction done inside a pole barn to make the MakerBarn a reality.
Continue reading “Maker Barn Organizer Creates Makerspace Access Control System”
RFID tags are really very primitive pieces of technology. Yes, they harvest energy from an RFID reader and are able to communicate a few bits of data, but for a long time these tags have been unable to provide useful data beyond a simple ID number. [CaptMcAllister] found a new RFID sensor platform from TI and managed to make a wireless pressure sensor that fits in the inner tube of his bike.
The sensor [Capt] is using comes from TI’s RF430 series that include a few neat sensors that don’t require batteries, but are still able to communicate sensor data to a cell phone or other RFID reader. With a pressure sensor, this tiny microcontroller can receive power from an RFID reader and send it back to a phone app, all without wires.
[CaptMcAllister] cut open an inner tube for his bike, epoxied his PCB to a patch, and sealed everything back up again. After a quick test for leaks, [Capt] found the data coming from the sensor was extraordinarily accurate, and should hold up well enough to be used in his bike.
You are at the corner store, buying gum. The cashier rings up the purchase, showing you the amount. You casually pull out your cell phone and wave it near the credit card machine, which beeps appreciatively. The cashier nods, and you walk out, stuffing gum into your face. What just happened? You used Near Field Communications (NFC) to send data between your phone and the credit card terminal.
NFC is a standard that allows two devices to exchange information over a short distance without being in physical contact. The two devices communicate using a weak magnetic field that, in theory, only has a range of a few centimeters, so both devices have to be physically close, and someone standing nearby can’t intercept or alter the signal.
Continue reading “Hackaday Dictionary: Near Field Communications (NFC)”
“We accept pain as a price of doing business, even if it is just for aesthetic purposes. You want to put a magnet in your finger, a doctor will ask you why; a mod artist will ask when you can start.” As with many other people who are part of the growing grinder movement, [Adam] has taken a step that many would consider extreme – he’s begun to augment his body.
Grinders – men and women who hack their own bodies – are pushing the boundaries of what is currently possible when it comes to human augmentation. They’re hackers at heart, pursuing on an amateur level what they can’t get from the consumer market. Human augmentation is a concept that is featured heavily in science fiction and futurism, but the assumption most people have is that those kinds of advancements will come from medical or technology companies.
Instead, we’re seeing augmentation begin in the basements of hackers and in the back rooms of piercing studios. The domain of grinders is the space where body modification and hacking meet. It mixes the same willingness to modify one’s body that is common among the tattooed and pierced, and adds an interest in hacking technology that you find in hackerspaces around the world. When those two qualities intersect, you have a potential grinder.
Continue reading “CyberPunk Yourself – Body Modification, Augmentation, and Grinders”