8 ms·
Control shopping cart wheels with your phone (2021)
Original DEF CON 29 (2021) talk: https://www.youtube.com/watch?v=fBICDODmCPI https://www.youtube.com/watch?v=fBICDODmCPI
- Liftyee 1y agoThis perfectly embodies the kind of hacker spirit that I love. Reminds me of the LoLRa project from cnlohr that transmits LoRa without a radio transceiver.
- deleted 1y ago[deleted]
- djmips 1y agohttps://cnlohr.github.io/lolra_talk/ https://cnlohr.github.io/lolra_talk/
- jmpman 1y agoI despise these wheels. About 15 years ago, my wife and I went to Target and first went to lunch at the far end of the parking lot. After lunch we headed into the store, grabbed a cart, now loaded with our newborn in his car seat, and our two year old sitting in the cart. A quick shopping trip later, we headed back to the car. When crossing the Target parking lot, the wheels locked up, in the middle of the road. Cart wouldn’t budge. Traffic all over the place, and now I have to pull both my children out, along with the shopping, and carry them all to my car. Pissed is an understatement. After my wife and kids were secured back in the car, I retuned to Target, complaining to the manager. A shrug was the best I received. Why did they need to put the wire in the middle of the road??? I hope someone attaches Bluetooth speakers to their shoes and locks every cart in target, so they have to remove the system.
- c22 1y agohttps://www.amazon.com/s?k=croc+speaker https://www.amazon.com/s?k=croc+speaker
- djmips 1y agowhaaa!?
- toomuchtodo 1y agoHuh, I wonder if it works if you play it over the PA system. https://hackaday.com/2016/03/04/social-engineering-your-way-to-the-target-pa-system/ https://hackaday.com/2016/03/04/social-engineering-your-way-... Edit: looks like an Ardunio can do this with PWM too
- fortran77 1y agoNo. That won't work. It needs the electromagnetic / rf field. It can work if your phone is nearby becaause of the " parasitic EMF from your phone's speaker to "transmit" a similar code by playing a crafted audio file" according to the article and the DEFCON talk
- deleted 1y ago[deleted]
- varenc 1y ago> I hope someone attaches Bluetooth speakers to their shoes and locks every cart in target, so they have to remove the system. Friends did this college in like 2005. Cambridge area, Shaws Market I think. I imagine the hardware setup was a bit different. All the details are hazy but I recall their lock transmission signal had a huge range and locked all carts in a wide area.
- MrFoof 1y agoBased on what's still around, likely the one (now rebranded a Star Market, same holding company) in Porter Square, right by Porter Square station. Based on what I recall, I believe there was one on the southeastern end of Green Street, a bit between Central and Kendall Square, barely northwest of MIT's primary campus area on the corner Massachusetts Ave and Vassar Street. That location has apparently closed in recent years.
- tecleandor 1y agoAround that year, or maybe even earlier, I remember reading an article about how to DIY one of those devices with a PIC microcontroller and wreck havoc on the store. It might have been something very similar to this: https://www.instructables.com/EMP-shopping-cart-locker/ https://www.instructables.com/EMP-shopping-cart-locker/ It might been the same text that somebody copy/pasted there, sounds vaguely familiar.
- alostpuppy 1y agoAvoiding these stupid wheels is probably the biggest reason I shop at Costco
- foresto 1y agoA market near me included the car park within their geofence, but did not include the (distant) bike racks or the route to them. Sigh... Never before has bringing a full load of groceries home been such an awkward hassle.
- 3eb7988a1663 1y agoAuthor's bio line says they are a "flat mooner". Which gave me quite a chuckle.
- MangoToupe 1y agoWhat's the meaning? Like, they have a flat ass?
- DrAwesome 1y agoThey're (jokingly) saying they believe the moon is flat. Like a flat earther, but the moon instead of the earth.
- ta8903 1y agoThey believe the moon is a flat circle (not a sphere).
- Dilettante_ 1y agoWhich is perfectly ridiculous. It's obviously carrot-shaped!
- Perz1val 1y agoWait, are you saying that what we see is just the tip?
- rokkamokka 1y agoOne half of carrot mooners believe it's the tip, the other half believe it's the butt. I'm a butt man myself
- WithinReason 1y agoWho are you who are so wise in the ways of science?
- tclancy 1y agoThat talk was incredible. Thanks for posting this and now I want to find them in the wild.
- al_borland 1y agoThe Kroger by my house as these (or ones that look very similar). I generally avoid that store for many reasons, but I’m tempted to go there just to try this out. This is a few years old now; I wonder if they changed the tones.
- mofunnyman 1y agoIf Defcon talks about hotel security have taught me anything, it will never be changed until the store is bulldozed to build a bigger store.
- jackson1442 1y agoThey have not, at least in my region, it's a fun little party trick when I see a locked cart out on the sidewalk.
- axiolite 1y agoYou can also take a wrench with you, to quickly remove the locking wheel from your cart. Maybe replace it with a non-locking wheel from another cart. Shouldn't be difficult to find carts left near or beyond the edge of the parking lot. I find the locking wheels annoying, because they're so often defective and make it a noisy struggle to get your cart through the store. But years ago I also had a neighbor in my apartment complex who would walk home with a cart every week, and would just leave (a dozen of) them there... she couldn't be bothered to push the empty carts back to the store, not even once. I'd think a $1 deposit/return system for carts would work better, and give the homeless in the area some gainful employment.
- mattmaroon 1y agoAldi does it for a quarter and it works pretty well to get people to return them.
- ijuz 1y agoBecause these physical quarters are way more valuable than $0.25. Where are you getting a new one from if you always pay by card?
- pavel_lishin 1y ago> Where are you getting a new one from if you always pay by card? By hanging around in an Aldi parking lot and offering to return the shopping carts for people.
- frou_dh 1y agoI'm a smartass that has a little metal paddle which can poke the coin slot and release the cart, but doesn't get retained by the slot.
- jjk166 1y agoYou know you can just go to the bank and get rolls of quarters.
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- asdfa456sdf33 1y agoI suppose now I can admit that we did this in college in 2003 (with RF, not audio), and had great fun seeing a grocery store descend into utter pandemonium, until the power electronics overheated and burned the signal carrier to whose chest the circuit had been taped, who started yelping in the store and drawing a lot of suspicion to himself.
- djmips 1y agoThat is pretty funny and an interesting scar to explain.
- Freak_NL 1y agoWhat makes this such a localised phenomenon? Locking shopping cart wheels just aren't a thing here in the Netherlands (or neighbouring countries). It used to be that most required a €1 coin inserted to unlock its link tethering it to the next car in the row, but then covid happened and a lot of shops simply disabled those locks and concluded that the system worked better without — probably driven in part by an increasing number of people who don't carry any cash. Losing a cart is expensive, but it doesn't seem to happen at the scale that would make a full blown locking wheel solution cost effective.
- isoprophlex 1y agoThere used to be a supermarket that had these near my student housing complex in Utrecht (the Netherlands). Only place I ever encountered them. This was 20 years ago tho. It was completely counterproductive, too. The edge of the zone was about 50% of the way home. Out of spite, we'd push the cart up to the edge, and leave it stranded there, carrying everything the last 200m ourselves. Not proud of that in retrospect; it goes to show that you can't stop assholes with technology.
- ars 1y agoIt's most common in places with lots of elderly or homeless, both groups find these carts very useful and will simply take them, homeless to keep, elderly to abandon near their home once they have transported their groceries. It's more also common in places where people walk, since it can be hard to bring groceries home on public transport. So yes, very localized. The shop near me doesn't have locking wheels (they used to, but stopped), instead they have a guy in a pickup that drives around occasionally, searching for carts.
- prmoustache 1y agoI understand about homeless people but elderly? Don't they have personnal shopping trolley? Like those with 3 wheels to be able to go climb curbs and small stairs? Regular carts are only used inside or by people who need to bring their stuff to their car and a pain in the ass to operate in the streets as they don't climb curbs easily. Locally all supermarkets actually have locks at the entrace so that people can lock their shopping trolleys next to the cashiers.
- stevage 1y agoI didn't watch the talk, but wondering if someone can explain this line from the post: > Since 7.8 kHz is in the audio range What is "the audio range" in the context of radio frequencies?
- jadamson 1y ago> Since 7.8 kHz is in the audio range, you can use the parasitic EMF from your phone's speaker to "transmit" a similar code by playing a crafted audio file The range of human hearing is about 20 to 20000 Hz. As a by-product of producing physical vibrations at those frequencies (i.e. producing sound) via an electromagnetic coil, a speaker will produce an EMF with the same frequencies.
- luca4 1y agoIt's not really because it's "in audio range" but rather "in a range which your phone speaker can transmit" which "happens" to be in audio/hearing range we can mostly hear for obvious reasons.
- yonatan8070 1y agoI believe this is referring to the human ear's frequency range, so 20Hz-20kHz, which is a range that phone speakers can produce pressure waves at. I didn't watch the talk either, but I'm assuming that one of the following cases is true: 1. The phone's speaker generates a small amount of EM intereference at the audio frequency it's playing at 2. The sound waves hitting the locking electronics cause them to vibrate at that frequency and pick up random noise from the environment as a signal. Either way, by using a frequency between 20Hz and 20kHz, everyone has some kind of "transmitter" that can generate mostly arbitrary waveforms.
- throw_a_grenade 1y agoHas several definitions, usually 20 Hz — 20 kHz: https://en.m.wikipedia.org/wiki/Audio_frequency https://en.m.wikipedia.org/wiki/Audio_frequency, but sometimes may refer to the range of specific codec (telephony might have something like 300—3400 Hz for example, so not this case). TFA means it as “I have a peripherial readily available”.
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- VoidWhisperer 1y agoNot sure if the original site owner will ever see this, but the hit counter they use (counter12 [dot] com) is flagged by Malwarebytes for phishing (and seems to have a history of popping fake virus links? [0]) [0]: https://www.reddit.com/r/neocities/comments/1i7di1c/help_fake_virus_links_on_my_site/ https://www.reddit.com/r/neocities/comments/1i7di1c/help_fak...
- PMunch 1y agoThey left their e-mail in the talk, in case you want to increase the odds of reaching them
- donatj 1y agoIs this the same mechanism for signaling lock/unlock as some moving sidewalks use to lock carts in place on the track to prevent you from pushing them? One of our local hardware store chains, Menards, have ramps in the form of moving sidewalks to allow customers to get fully loaded carts between floors safely and they seem to very reliably lock to the floor at the start of the ramp and unlock at the bottom. I've always been curious about the mechanism.
- athenot 1y agoThat's a different mechanism. There are rubber "feet" at the bottom the of the carts. The wheels are thin slices that sink into the moving sidewalk grooves, therefore the cart rests on the feet instead of the wheels. It's a passive mechanism, there's no actual locking of the wheels. (Try lifting the cart to see that in action.)
- MarkusWandel 1y agoOne unintended consequence of these locking shopping carts is flat-spotted wheels from where they skidded when they locked. Thumpa-thumpa-thumpa through the store, rats, got another bad one.
- Slava_Propanei 1y ago[dead]
- stronglikedan 1y agoNitpick, but a warning in dark green text on a light green background at the very top of the page where no one really looks .isn't really a warning.
- orbisvicis 1y agoHah, this actually works - bookmark payed off! There is one large grocery store near me as well as two higher-end ones. The higher-end ones banned in-store bicycles last year. The large chain store banned them just recently. The area has a lot of car/bicycle thefts and unfortunately the only bike rack near the large one is 30 feet over the property line. Now I no longer have to play a river-crossing puzzle to bag my groceries. As a matter of protest I will be leaving the locked cart near the bicycle rack (but also because an unattended bicycle full of yummy food is begging disaster). You have to be about 6 inches away for it two work. There are two locks that operate in tandem but sometimes you have to play the tone for both. Also the property line is in the middle of a lane, so a mild safety hazard.
- orbisvicis 1y agoIt has occured to me that rather than the complex instructable linked below, it might be easier to purchase an off-the-shelf BTL (high voltage => greater power) amplifier to drive 2W over a small (0.3m dia) air-loop antenna. The AC input signal from the phone's USB DAC is about 0.77V RMS. Let's power the amp with two consumer off-the-shelf 9V batteries in series (18V). Assuming ~1-2 (1.5 here) ohms of internal resistance, the total current draw should not exceed 250mA or the voltage will drop below 8.6V. The loop antenna therefore needs 10 ohms of impedence, and a tuning capacitor to make it resonant (fully resistive). The AC signal needs a coupling capacitor to remove any DC component, followed by a bias resistor to tie the amps signal input to ground. Each amp signal output needs a coupling capacitor because no way will I be able to correctly calculate the tuning capacitance correctly, and also because the antenna won't be a fixed loop. The most efficient use of those 10 ohms is with litz wire, which at 20 awg comes to 300 meters with a 450nF tuning capacitor... which is not happening. Let's shoot for 30m of 20-awg non-litz wire and make up the difference with a 8.8 ohm resistor. 2w across 32 coils @ 10 ohms corresponds to 0.45 A, which at a meter's distance comes to about 0.6 uT... ridiculously tiny. Will it work to activate the circuit? I don't know. However this antenna is simply wasteful - it would be better to switch to a ferrite core design. The magnetic moment of a ferrite core increases more with coil diameter than coil length... but to target 10 ohms resistance at resonance might require a coil length greater than diameter. I haven't really looked into it. To conserve battery you need an amplifier with a shutoff pin. These are always logic pins (DC on/off), which entails a diode/capacitor/resistor combination tuned to detect and convert AC input to on/off with a configured decay time, i.e. keep the amp powered on for X seconds without signal. Unfortunately the logic pins require high voltage relative to the power source (battery) and 0.77 Vrms just won't cut it. This then entails adding a transistor to shunt power to the shutdown pin from the battery. Then I had a look at a sample schematic of the TPA3116 amplifier, and there are so many pins to wire. At this point the project isn't any simpler than the linked instructable. Then I found this: https://www.rockvilleaudio.com/headrock/ https://www.rockvilleaudio.com/headrock/ According to the website it requires a minimum load of 16ohms, but that might be ideal for ferrite-core antennas. Perhaps I'll give it a try!