[HN Gopher] Wearable Microphone Jamming
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Wearable Microphone Jamming
Author : RandomGuyDTB
Score : 135 points
Date : 2020-02-19 17:30 UTC (5 hours ago)
(HTM) web link (sandlab.cs.uchicago.edu)
(TXT) w3m dump (sandlab.cs.uchicago.edu)
| mdszy wrote:
| Sure it's "wearable" if your definition of "wearable" is
| incredibly loose.
| __ryan__ wrote:
| It's only "wearable" if your definition of "wearable" doesn't
| take into account style. I mean, come on! The space age design
| wouldn't pair well at all with my wardrobe. Can you imagine
| that clunky thing over the cuffs of my Ralph Lauren suit
| jacket? Rating: 0/10. under no circumstances would I don that
| monstrosity.
|
| Edit: sorry, I went against my better judgement and decided to
| respond sarcastically to the other comment. I was being
| facetious.
| diego_moita wrote:
| Are you both sure you understand the difference between the
| terms "proof of concept" and "final product"?
| mdszy wrote:
| I'm sure of exactly zero things.
| kempbellt wrote:
| You sure about that?
| mdszy wrote:
| Nope!
| kryogen1c wrote:
| OBO
| doublerabbit wrote:
| I would and I actually quite like the design. Sure it's a
| prototype, but if you have a netHacker theme going it'd look
| rather dashing.
| falcolas wrote:
| Another discussion of this:
| https://news.ycombinator.com/item?id=22339548
| alasdair_ wrote:
| A similar effect occurs when using infra-red LEDs near the face
| to prevent video recording. The problem is that many phone
| cameras now have a UV/IR filter - I can see microphones having a
| similar setup to improve sound quality in the future.
| elric wrote:
| All CMOS cameras have an IR filter, for reasons that have
| nothing to do with people using IR LEDs to fool (some) cameras.
| In fact, removing the IR filter and replacing it with a visible
| light filter is a cheap way to turn a cheap webcam into a
| (crappy) night vision camera.
| sigstoat wrote:
| the original paper on jamming microphones and/or using them for
| covert data transmission:
| https://synrg.csl.illinois.edu/papers/backdoor_mobisys17.pdf
|
| it seems to me that this is largely an attack on common
| preamplifier circuitry. would it be sufficient to ensure that the
| preamps implement low pass filtering? or is the issue more in the
| microphone element?
| neetdeth wrote:
| From the paper linked:
|
| "For the above idea to work with unmodified off-the-shelf
| microphones, two assumptions need validation. (1) The diaphragm
| of the microphone should exhibit some sensitivity at the high-
| end frequencies (> 30kHz). If the diaphragm does not vibrate at
| such frequencies, there is no opportunity for non-linear mixing
| of signals."
|
| The devices tested include hearing aids, smartphones, smart
| watches, etc, which are all likely to include small surface
| mount MEMS microphones. I doubt any of these techniques will
| work against a larger dynamic or condenser microphone, where
| the mass of the diaphragm makes the system inherently
| insensitive to ultrasonic frequencies. There's a reason the
| jamming signal is inaudible, and it's not because our auditory
| cortex contains an ideal lowpass filter.
| ampdepolymerase wrote:
| More interestingly covering the mic with a fabric can dampen
| the jamming signal.
| VectorLock wrote:
| Would this hurt people with cochlear implants?
| martyvis wrote:
| Or any hearing aid? That said, hearing aids in particular
| employ circuitry specific tuned to only amplifier the desired
| sound and frequency range intended to be heard, modern ones
| having profiles for normal speech, congregations, music, etc.
| rahuldottech wrote:
| Yes.
|
| > _Yikes, please don 't do or encourage using these in public -
| there are many accessibility devices (hearing aids, cochlear
| implants, etc.) which depend on MEMS microphones to function._
|
| > _You could inadvertently make the world much worse for people
| who already have a difficult time of things. Imagine carting a
| cellular and WiFi and bluetooth jammer around outside of a
| Faraday cage - it 's insanely irresponsible and inconsiderate.
| _
|
| From the top comment here:
| https://news.ycombinator.com/item?id=22339548
| nonbirithm wrote:
| It would be a loss if due to a critical need to protect
| privacy we end up inadvertently harming a group of people
| that are already at a disadvantage. I once knew a hearing-
| disabled person and the hardship it brought them affected
| nearly every interaction with them I had. For me that trade-
| off is not worth it.
|
| If the best channel to help the deaf listen clearly is also
| the best one for letting eavesdroppers listen clearly, then
| this is a problem best not handled with such a heavy handed
| solution - possibly not even a technological solution at all.
| frandroid wrote:
| Stylish!
| vorpalhex wrote:
| This is really neat work. I'm curious to see if smaller and more
| portable versions of this can be made - obviously a prototype is
| always going to be bigger and be relatively limited. Now that the
| research has been surfaced, this appears easy enough to follow so
| it'd be neat to see how electronics enthusiasts run with it.
| ct0 wrote:
| Do cell phone speakers operate at this frequency range as well?
| I could imagine an app specifically focusing on responding to
| the words "to be safe", by turning on the white noise maker.
| btbuildem wrote:
| Is sound of that frequency naturally directional? Wonder if an
| omnidirectional driver / sound source could be used to prevent
| the "dead spots"
| squarefoot wrote:
| The interesting parts are those 25KHz transducers which seem
| identical to the 40KHz used since likely forever in ultrasound
| remotes and more recently in collision avoidance sensors for
| robotics. I did a small search and found mostly high powered ones
| at that frequency, probably ultrasound cleaners spares, or
| smaller but a lot more expensive transducers compared to 40 KHz
| ones. Does anyone know of a source for these transducers?
|
| I also wonder if a simpler approach could be used since the
| purpose appears to be (can't understand the math) generating
| noise by driving randomly a number of oscillators around the
| transducers resonance frequency then induce subharmonic
| vibrations into the MEMS mics through etherodyne operations
| between these sounds. If that's how it works, then the DDS chips,
| the Arduino and the code might be swapped with a less random but
| likely equally functional set of dissonating oscillators
| modulated by LFOs (all doable with plain old logic gates); not
| unlike the old school way of generating cymbals metallic sound in
| analog drum machines. Here's the Boss DR110 relevant schematic as
| an example.
|
| http://www.sdiy.org/richardc64/new_drums/dr110/dr110a1.html
| shanxS wrote:
| Can someone please explain what is stopping these recording
| devices (Alexa/phone/etc) to filter out ultrasound?
| kube-system wrote:
| Absolutely nothing other than the fact it wasn't a requirement.
| stefan_ wrote:
| As I understand it, they of course already filter it out, but
| filters are imperfect and it bleeds in at the cutoffs or
| aliases.
| shanxS wrote:
| I see, so it's matter of time before off-the-shelf
| microphones become technically advannced enough to counter
| this.
| falcolas wrote:
| Perhaps, though not easily. You could be looking at getting
| harmonics on the physical components of the microphone from
| the ultrasound which would bleed all the way through the
| normal sound ranges. Plus, with enough sound pressure, the
| microphone may be physically maxed out (that is,
| physically/electronically unable to register any further
| sound pressure).
| elicash wrote:
| Is it?
|
| Seems like countering it might be a use-case only important
| to specialty buyers who want to get around this kind of
| protection. Even if it wasn't that difficult to counter,
| there might not be enough incentive for most off-the-shelf
| mics and specifically Alexa/phone/etc to do so.
| moftz wrote:
| It's not an advancement thing, its a cost thing. They made
| the filter good enough to block out the stuff people can't
| hear but this device is super loud so you would need
| additional layers of filtering to completely block it.
| Smartphone mics need to be tiny so additional analog
| filtering is going to take up space and resources. You
| could also run a higher sample rate on the ADC that
| converts the sound to a digital signal and run a digital
| filter to cut off the ultrasonic band but that requires
| more power and chip resources and the ADC might need to be
| swapped for one capable of the higher sample rate. The
| tools are all there to defeat this but it's a matter of
| reducing power, cost, and computing resources.
| [deleted]
| wadkar wrote:
| How will this impact calls? If somebody is wearing this in a
| public space then any callers in surrounding area will have
| problems, no?
|
| It would be interesting to evaluate this device's impact on
| telephonic conversation!
|
| I hope there is a switch to turn the device on/off. Otherwise you
| won't be able to talk on the phone :-)
| devb wrote:
| It's already been tried!
|
| "During a phone interview, Mr. Lopes turned on the bracelet,
| resulting in static-like white noise for the listener on the
| other end."
|
| https://www.nytimes.com/2020/02/14/technology/alexa-jamming-...
| bmgxyz wrote:
| I think this is a neat idea, but I suspect it would be more
| useful as a standalone device than as a wearable. Devices like
| this could be installed in secure rooms or deployed on the fly in
| discreet locations with a high rate of success, I'd guess. Arrays
| of them could work together for better coverage.
|
| Still, this may be the only real option in public spaces (i.e.
| outdoors). If you're okay with people knowing that you're trying
| to avoid being recorded, then this would probably be fine.
| tsumnia wrote:
| I envision a variation that sits in the corner of a room,
| similar to how a fan operates, gradually turning the speakers.
| However, as others mentioned, I'm curious over the effect it
| would have on hearing aids, etc. Secondly, if there a variation
| of this device that could straight up disable WiFi?
| moftz wrote:
| You could just have a simple Wifi deauth beacon. You can do
| it with a simple ESP8266 and could either kick everything off
| the network or target blacklisted MAC address ranges. It's
| usually illegal to do this to someone else's network just
| like running a real Wifi RF jammer.
| BeefySwain wrote:
| Jamming wifi (as well as many (most?) other frequency bands)
| is very simple and very illegal.
|
| https://en.wikipedia.org/wiki/Radio_jamming
| tsumnia wrote:
| Right, that'd be my concern - that if their implementation
| could be modified in a similar manner to create jammers
| that would be quick to deploy but difficult to locate.
| Defenestresque wrote:
| They mention that the wearable component was a conscious design
| choice to overcome certain limitations of standalone devices:
|
| (On standalone device limitations)
|
| >(2) They rely on multiple transducers that enlarge their
| jamming coverage but introduce blind spots locations were the
| signals from two or more transducers cancel each other out. If
| a microphone is placed in any of these locations it will not be
| jammed, rendering the whole jammer obsolete.
|
| >To tackle these shortcomings, we engineered a wearable jammer
| that is worn as a bracelet, which is depicted in Figure 1. By
| turning an ultrasonic jammer into a bracelet, our device
| leverages natural hand gestures that occur while speaking,
| gesturing or moving around to blur out the aforementioned blind
| spots.
| moftz wrote:
| They make it a wearable to counteract the nulls caused by the
| multiple speakers. Random movement causes the nulls to not stay
| in one place for very long, limiting how much of a word or
| sentence a microphone could pickup. You could build a phased
| array of these that could quickly move a hotspot of ultrasonic
| noise all over the room. You could them position on the ceiling
| with a fixed radius between them to make sure that the highest
| pressure occurs at about waist level, where phones in pockets,
| smart watches on wrists, and smart speakers on tables would
| reside. Another idea would be a ball of these in the center of
| the room and have it move up and down to get the best average
| coverage around the room.
|
| Smart assistants are usually not recording really high quality
| audio, it takes more time to process it and more time to send
| it back home so they are going to a lower sample rate than
| typical voice recorder app would use. Siri uses a 16KHz sample
| rate (Fs=16KHz) which is enough to put the whole human vocal
| range in the 1st Nyquist zone (less than Fs/2). Playing a sound
| at 26KHz (3rd Nyquist zone, >Fs but <1.5*Fs) is going to cause
| a reflection across Fs. So the 26KHz tone, sampled at 16KHz,
| creates a tone at 10KHz which could be enough to confuse a
| naive implementation of a smart assistant. Ideally, you want
| fix this by either installing an analog filter so the
| ultrasonic noise can never reach the ADC or sample the whole
| range (up to 44.1KHz is a good start) and filter digitally.
|
| There is a paper called DolphinAttack [1] where they attempted
| to use the ultrasonic audio band as an inaudible attack vector.
| You could play an ultrasonic noise that no one can hear except
| for the smart assistant.
|
| [1]
| https://gangw.cs.illinois.edu/class/cs598/papers/ccs17-hidde...
| lovetocode wrote:
| And this is also likely very illegal...
| Polylactic_acid wrote:
| Would it? I'm not aware of any laws about sound that wouldn't
| bother the human ear. The closest thing I can think of is laws
| about RF jamming but this clearly isn't a radio frequency.
| kylek wrote:
| What could go wrong with blasting out ultrasonic noise in every
| direction? (Besides a lot of confused dogs...)
| goda90 wrote:
| A lot of confused hearing aid users.
| sbradford26 wrote:
| Currently wearing noise cancelling headphones and wondered
| what would happen with them, but hearing aids would be a much
| bigger concern. I would wonder if since hearing aids are so
| focused on human hearing that they would have filters that
| would block out any sounds outside the human hearing range.
| LinuxBender wrote:
| Starving bats. Bats keep moth and mosquito populations down in
| some areas. They use ultrasonic acquisition of their prey.
|
| Rodents less likely to nest near you may be a positive thing.
| asdfman123 wrote:
| I can see this being useful for blocking your smartphones and
| Alexas, but it seems like devices specifically designed for
| surveillance could start being designed to fix this exploit.
| fyz wrote:
| This might result in jammed audio for human listeners, but
| recovering the original audio seems like a fairly mundane signals
| extraction problem subject to the standard signal/noise ratio
| issue.
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