Three weeks ago I reverse-engineered my garage door opener wireless protocol. I probed the remote's PCB with a Saleae logic analyzer and found it was a 12-bit code ASK-modulated at 390 MHz with bits encoded as sequences of 10 kHz and 20 kHz pulses. I bought a $13 spare remote to hack it and control the RF transmitter section from my computer through an FT232 sending the ASK signal. I just cut off the digital signal trace going from the MCU to the RF transmitter and hooked it to the FT232. I built a brute-forcer and it works quite well. I do not have my notes at the moment, but IIRC one code takes 25.6 ms to be sent. And my manufacturer (Genie) seems to require the code to be transmitted 4 times consecutively to open the door, that's 102.4 ms. Multiplied by 4096 combinations, this gave me a brute-forcing time of 7 minutes.
I had tried Samy's exact attack to reduce the brute-forcing time but it did not work at the time because I tried it before I discovered the code had to be sent 4 times consecutively (5 times makes it more reliable due to RF interferences). So I am not surprised to see Genie absent from the list of models Samy found vulnerable.
But I should try to find out the longest period of time during which these 4 repetitions of the code need to be sent. Maybe it does not have to be perfectly consecutive, but it could be 4 codes received within an interval of 200 ms or 1000 ms. If so it might still be possible to build a modified De Bruijn sequence that repeats codes 4 times while being only 4 times longer.
By the way it is very surprising a description of the 12-bit Genie protocol does not appear to exist online. These remotes are so easy to reverse engineer, so common (Genie is in the top 3 or top 4 most common openers), and so old (the protocol has existed since 1985), you would think there would be information about it online, but nope.
PS: I wonder if there could be commercial interest in cryptographically secure garage door openers? A $0.50 ARM Cortex-M0 MCU is all you need to implement a HOTP based on HMAC-SHA1. Then a simple learning/pairing system writing the key in EEPROM can even sustain the battery being removed from the remote. But there is probably no interest... which is why most remotes are insecure even the "rolling code" ones.
Well, it seems that from the point of view of Genie, if it's required to send the correct code N times in a row, acceptance should be aborted if that is interspersed by any wrong code. In that case, a De Bruijn sequence wouldn't work.
Because noise and interference. You don't want the neighbor opening his garage door to abort yours--your code and his would be interspersed, but you both still want your door to open.
FWIW, this sounds like a hook around building a business for "next-gen" garage door openers. Security, quality of build, and convenience are among the factors that could be pitched to early adopters. Heck, this even feels like something that the right small team could work into a really sharp Kickstarter pitch, if so inclined.
One tricky problem is that garage door openers tend to "just work" for a long time. Over and above cost, upgrading is a much larger installation hassle, far larger IMO than e.g. Nest thermostats had to overcome. All of that will limit adoption rates, even for willing early adopters. A retrofit angle would help, akin to the retrofit-smart-deadbolt market.
An "interesting" sales objection would be this tech not working with cars that have built-in recording garage door remotes (vaguely similar to home theater smart remotes, for those unfamiliar).
Which is only as secure as the door frame it goes into, which usually means: pretty insecure.
Still, I agree with the premise that it's about assumptions, and if people can be made to realize that their garage door openers are inherently pretty insecure, and feel that that presents a substantial, then there's a market there. But until it becomes a problem that's common enough for media outlets to scare people about it, there probably isn't a large market yet.
(Any marketing plan for an endeavor like that should have a PR budget from day one, since that's exactly how such stories tend to become news segments.)
> Which is only as secure as the door frame it goes into, which usually means: pretty insecure.
But the door frame/deadbolt is still more secure than the remote controlled garage door because abusing the former mode of entry is more likely to draw concern from passers by and leaves a permanent record of your passage.
I think that's one valid way of looking at it, and many technically-inclined people would be inclined to agree, I'd imagine.
But another way of looking at it, and one I suspect most non-technical people would, is that it just takes one motivated person of roughly-average strength to break a doorframe. It takes someone with fairly uncommon technical sophistication to make one of these devices.
Once someone mass-produces them and sells them in real volume that perception could flip, but right now I'm far more concerned about a flimsy doorframe–which leads to where I live and sleep–than I am about someone rigging up a way to open my garage door–which only gets them into a detached garage where insured stuff is kept. The odds of a break-in being by force (whether against a door frame or a window) are just vastly higher.
Around 10 years ago, I bought a house that had two garage doors and each door had it's own separate remote and each were the insecure fixed-code kind.
I was able to easily wire-up a replacement receiver to the opener unit that allowed me to update them them to rolling code systems that were more secure and would allow me to control both on one remote. I remember it being a bit clunky, in that I had to plug the receiver into a wall outlet and run a wire back to the opener unit (I think most newer homes put in outlets in the ceiling for the opener to plug into, but this one was directly wired into a ceiling box), but it wasn't very hard to install and was a lot better than having to replace the entire unit!
Somewhat of a tangent, but I am concerned about the MITM attack on car locks [1]. This kind of attack is being used in my neighborhood in Oakland, California and no doubt other places. I read the reports of "someone is breaking into my car but no windows/locks are broken". Then a couple other people on NextDoor chime in with the same thing and one person reports a woman who is walking around the neighborhood and appears to be the one responsible. A coworker explained a method where one can amplify the signal of the car and/or car key so that the car thinks the key is next to the car and the door unlocks.
The cryptographically secure garage door opener is still susceptible to MITM if the MITM attack is being done purely by amplification of signal, right?
It's almost like the key needs a handshake with the car by some method that is not using radio frequency. I wonder what options that leaves open? So far, I have not thought of one that is convenient (at some point, it is easier to go back to using a physical key to open a physical lock after all).
1. I think there was a post about it here already but I couldn't find it.
Yeah, a car's passive entry system can definitely be exploited by relay attacks. Here is an academic group who demonstrated it: https://eprint.iacr.org/2010/332.pdf
The most obvious way to mitigate is to have the car require the key to send the first bit of the response at most N nanoseconds after the last bit of the challenge is sent over the air. Because of the speed of light this assures the key is within a certain distance of the car. Ideally you want to constrain this to ~2 meters since passive entry requires the driver to touch the door handle. This limit is not to be confused with remote keyless entry which should work up to ~100 meters as it requires the driver to actively press a button so, like garage door openers, this is not vulnerable to relay attacks. However power-constrained MCUs, especially in the key, have a hard time computing a strong cryptographic challenge within N nanoseconds with N low enough, hence the problem...
After my little foray into garage door openers I am currently looking into implementing relay attacks on the passive entry / passive go system of my car (2012 Audi). Fascinating stuff.
There are super low power accelerometers with wake on movement. Simply require the key be recently moved about to activate the door. If the key is not awake, it can't answer any challenges.
You don't need to compute the challenge in N nanoseconds. Instead, the car could send a challenge, the key can compute it in however much time it likes. Then the car sends a one time pad, the key receives it and xors the otp with the challenge's response. Then it sends that.
The cryptographic challenge makes it secure, the XORed one-time-pad allows for fast measurement of the round trip time.
Was thinking about making the same comment. People throw cinderblocks here to get garage doors open. Until recently, we deliberately kept ours unlocked (if we're going to get burglarized, at least we'd like to keep the doors on the hinges).
I had to do that when I worked in San Francisco. I just left it open with a note, "Please take a nap in here, whatever, just don't break anything." I did put a kill switch in that mechanics can't figure out. It wasn't the stupid radio I cared about, it was repairing the windows.
But breaking a window and climbing though it takes time and you can cut yourself if you hurry and crowbar makes a lot of unwanted noise.
And not every garage is your basic suburban-attached-to-a-house type. Some little more expensive flats have underground parking where the gate opens with garage opener and thous suckers don't even have windows, they are just metal gate.
With this you could gain access to the cars and with boosting the signal from the cars with the "keyless entry" you could easily swipe clean a lot of cars without the a trace.
>> I wonder if there could be commercial interest in cryptographically secure garage door openers?
>Probably not. Mainly because breaking a window or crowbarring a door is a lot less expensive and a lot faster.
It's also a lot more likely to attract attention of bystanders.
Another concern may be insurance. In my area of the world, insurance companies generally refuse to pay out for burglaries unless there is evidence of a break-in (a broken window, forced door or something like that). This would likely not be covered. If this kind of device became popular with thieves like the car keyless entry hacks have, I can see there being a demand for something like this.
We're already seeing organized theft rings using devices to unlock car doors without breaking in. I don't think it's outside the realm of possibility for the same thing to occur with garage doors.
A friend who lives in a wealthy neighborhood here had their garage broken into electronically more than 10 years ago. So clearly some people have known about it for a while. The local police claim the thief probably "listened" to their garage door opener open the door at least once to get in, as opposed to brute forcing it.
It's not uncommon for thieves to go to open houses in nice neighborhoods when a property is for sale & copy the dip-switch codes. This also happens when homes are under construction. No one ever thinks about changing their garage door opener code.
It's also pretty common for garage door installers / builders to either not change the default config or use the same one or pattern for every home. We were amongst the first to build a house in a new sub in our area so we'd go for walks around the neighborhood while the homes were being built and would go through them and of course I'd always look at the codes. The primary builder in the sub set the dip switches to the number address of the house. That provided a nice geeky / awkward way for me to introduce myself to my neighbors by opening their garage doors for them.
By the way it is very surprising a description of the 12-bit Genie protocol does not appear to exist online.
Look at the datasheet for the IC they use. 2^12, as it's known, is a very common code and the ICs out there implement only a handful of variations on it.
The other common variants are 3^9 (19683 codes), 3^12 (531441 codes) and 3^18 (387420489 codes).
The remotes I reverse-engineered were universal ones with generic MCUs, so their datasheets weren't useful: Skylink model 69 with an EM78P468N, and Skylink model 39 with an HT48R30A-1.
A bit of a shame that they used an MCU instead of an encoder/decoder ASIC, since they could've implemented something better. The fixed-code remotes I've seen use a standard IC like an HT12E.
If those weren't OTP/mask ROM, reflashing them with a different firmware (maybe even a simple rolling code?) could be an interesting exercise...
Wouldn't it be simplest to refuse more than 4 attempts per minute? I suppose it would sometimes frustrate the owner bungling the code, but stretching out brute-forcing the whole space to hours instead of minutes would make it a lot less appealing to would-be thieves...
I forgot to mention a crucial piece of information why De Bruijn sequences couldn't possibly work against Genie. The packet the remote sends is made of a 4-bit header followed by the 12-bit code, but the header is using a bit encoding (sequence of 10 and 20 kHz pulses) that couldn't possible represent a valid sequence of 0s and 1s in the code. So yeah, unless you can trick a Genie receiver to parse a code without the header, De Bruijn sequences can't work.
Did stuff like this when was a kid, but just used a binary counter hooked into the switches on the replacement remote. What I really wanted as a huge RF amplifier so I could broadcast the signal 5+ miles in all directions.
Exactly like computer security, it's not about making it impossible to gain entrance[1], it's about making it both inconvenient enough and require enough skill that it takes longer or is more noticeable, making it more likely the intruder will be noticed, thus raising the likelihood they will be caught.
That said, a few seconds is a pretty low bar. Commodity locks should be better than this, for all our sakes.
1: This applies to anything where someone has access. It's trivial to come up with ways to secure things that need no ingress/egress whatsoever.
I don't know what's normal now but a long time ago, 1997, I moved with a complex with 300 garages each with a remote. I opened the remote to change the battery and noticed only 8 switches for the code. 256 codes, 300 garages, drove around the complex opened 2 other garages. Even at 12 bits with 300 garages the odds are very high of a match
While locks don't keep skilled criminals out, you'd be shocked how many unskilled ones there are. Meth/crackheads routinely go around twisting doorknobs in apartment complexes or pulling on car handles just hoping to find something unlocked so they can steal whatever is there. They (usually) don't break and enter, but if they happen upon an unlocked door they'll walk in and steal anything.
Not that this is a common attack, but to add to the stew - I knew a guy who left his leather jacket in his car, which was a soft-top convertable. The jacket thief simply sliced open the top and took the jacket.
These days I just tell people to consider the inside of their car a public place, and never to leave anything in there that you wouldn't leave lying on your front fence or similar. There are simply too many ways for people to get into cars to win that game, and ultimately, few things will stop a thief who's willing to damage the car (hammer through a window, or knife through a soft-top, for example).
That's not exactly like computer security. With computer security you plan for the worst, not the average. That's why even a skilled hacker/coder can't break into banks or major websites on a daily basis.
A bank is not equivalent to your home. You may note that banks generally lock up their physical money behind very sophisticated security systems (relative to other homes/businesses). They deal with a different level of threat, and respond accordingly. Even then, they don't try to safeguard against someone physically demolishing the building, because there's only so much they can do, and at the point someone is willing to go that far, the chance they will complete the theft without being noticed and tracked is virtually non-existent.
Exactly. Lots of people don't realize that most of their door locks are there to keep "normal" people out, because dedicated criminals are typically going to find a way in.
Locks reduce the instances where dishonest people can exercise dishonestly without repercussions. But that's what much of life is about, reducing the occurrences of negative outcomes. Elimination often isn't possible or feasible.
This is a much more accurate than the old "Locks keep honest people honest" saying.
If you consider yourself an honest person, ask yourself how many times you've tried to open doors to random houses as you walk down the street. If you found it unlocked, do you rob the place?
If you need a lock to keep you honest, you may want to reevaluate your values.
The phrase is rooted in a very old memeplex, the part where religious morality and sociopathy overlap. Most ideas revolving around the concept of "putting the fear of God into someone" aren't actually for regular people with empathy. They're for sociopaths. It seems that sociopaths used to be seen as just completely normal people, undifferentiable from everyone else—and much of "morality" is actually an attempt to create extrinsic incentive systems to replace the thing that sociopaths lack, so they can seemingly function normally.
That's all to say, by analogy: locks are to keep honest-acting sociopathic opportunists honest-acting.
Right, you're exactly right, but you also seem to know a bit about sociopaths, and so it surprises me that you are implying that we don't see sociopaths as normal people these days. I've had very personal run-ins with real, genuine sociopaths in my life, and most people just have no idea that there are these people just totally walking around being treated like normal human beings. Sociopaths are not human beings, I say, because what is humanity but our empathy? And sociopaths do not have it, ergo...
The counter-coat-hanger-ziptie method is great, and I use it. But for the sake of safety, I recommend a thin ziptie - something that would break under the weight of an adult. It's still plenty strong enough to prevent the door being un-coupled by a coat hanger, but weak enough that an adult (inside the garage) could make an emergency exit.
Bumping always mystified me, in a sense that as I've understood it its for pin tumbler locks, so why do people use them? Every place I've lived has had Abloy locks (which no doubt have their own problems), but as far as I know they at least can't be bumped.
Kwikset has almost completely gone to their new SmartKey system, which uses wafers, and is harder to bump. It has other vulnerabilities, but bumping isn't one of them.
Wow. That's hilarious. The vast majority of all garage door openers now sold are rolling code, but I bet almost all of them will fall to the coat hanger method.
The Wikipedia article doesn't mention this, but the de Bruijn sequence can be computed greedily.
Start with 000...0, keep appending the largest digit possible that doesn't produce a code that's already been used and you'll go through all the codes.
The "De Bruijn sequence". I was wondering what that was called, since I realized it's optimal for creating IFS fractals. I figured it must have a name. Yay!
Which should I consider more insecure: my garage door, or the deadbolt on my front door? I wonder how commonly lock picking is used in crimes. I've picked a lock before myself, but I have no real idea how effective locks are in stopping people that want to commit house thefts.
I expect an automated garage door opener is much easier to use than a lock pick though, and probably easier to produce and distribute than lock picks. So I shouldn't consider garages as secure.
My parents did the thing where they put keyed deadbolts on all of the doors. So when someone wanted to break in they broke the glass on the door, discovered the deadbolt, broke the glass on another door and discovered the deadbolt, then broke the glass on a third door before yet again being foiled by the deadbolt. Then they broke a window and stole our stuff anyway. Apparently they were professional thieves too, since they were hitting half a dozen houses each day while driving through the state. The cops finally caught them when they were pulled over for driving on expired tags or something stupid. They had robbed over 100 homes in two weeks before they were caught.
The only thing the deadbolts did was to make us replace three extra windows.
About 15 years ago, my aunt stopped locking her convertible. She used to, but people would slit the closed top to reach in and unlock the door to look for CDs and such to steal. A few hundred bucks to replace the top was way worse than losing some change and such. Then she switched to a late 90's Miata which had a lockable center storage bin/arm rest.
A buddy of mine did this in his '70 Karmann Ghia, which, even if the door was locked, was easy to break into with a belt through the window that didn't roll all the way. Someone still broke the window and tried to steal the broken cassette deck that was in it. This was in the late '00s, so I'm not even sure what they were going for there. That cassette deck couldn't have been something you'd even readily be able to give away.
Seriously, a dog[1] apparently is a way better security system.
[1] Big dogs are not afraid, thus they sleep at night if not properly trained. Small dogs (especially Yorkshires) are the most bad-ass security system I've encountered. They bark on anything alive that comes into 0.5miles circumference.
In order to gauge the severity of any potential threat, you have to time the barking interval. If it lasts longer than three minutes, there may be armed men outside your door. Or they have to pee. So when you open the door to let them out, the thugs can enter.
Not really. If you're looking for home security, get a terrier. They are high on loyalty and low on fear, so if they are barking, there's probably a non-packmate animal around. Some were bred to chase badgers down into their holes and kill them, after all. They're anything but timid.
Pit Bulls are terriers, and one reason they are so popular for lower-income city-dwellers is the manageable danger they present to unauthorized, non-packmate intruders in their range. You do not burgle a house with a Pit Bull or Staffordshire in it, period. And you think twice or thrice for any other type of dog. The fences, warning signs, food, vets, and boarding are very often cheaper in the long run than professional alarm system monitoring or contents replacement insurance.
> Which should I consider more insecure: my garage door, or the deadbolt on my front door?
Your garage. Such attacks can be done remotely, sitting in your car. You can open the garage door; hang around for a while, and then casually saunter in. But an attack on the front door requires physical presence at the door, and hence easier to detect.
Criminals use lock picks when you don't want someone to know that they broke in. Most criminals are the "snatch-and-grab" type. They are more likely to look for an unlocked window or just break a window.
So true. I once lived in an apartment block where a lot of the other apartments on my floor were burgled one day.
The locks did.. nothing. The thieves simply kicked the doors until they splintered at the lock. In fact, one door even snapped clean in half, so it ended up looking like a stable door, with a lower bit no longer attached to the lock which was now opening freely.
I'd wager it took them a similar amount of time to do this as picking a lock would have taken for someone experienced, and with far less training.
It taught me a very practical lesson about security. You can spend a lot of energy engineering the perfect lock, but always be aware that there will likely be obvious (once they've happened at least), perhaps very course, hacks which make that brilliant lock totally redundant.
The parallels to software security are obvious. To loosely quote Richard Campbell, it doesn't matter how strong your password is, if a truly determined bad guy wants to get at your data, they'll just use a wrench ;-)
No housebreaker with an ounce of brains would use a lock pick before trying a bump key first. The locks on your house are almost certainly bumpable. The locks at your workplace might be more secure.
That's fine, though. If you make the lock on your front door more secure, the weak point is now the latching mechanism, the door frame, or the door itself. Or perhaps it is your sliding patio door, that can be levered. Maybe you left a window unlocked. Or your garage door has a code that can be MITM'ed or brute forced.
The thing that saves most people is that there is really nothing worth stealing in their house. If a fence pays 10% of retail for stolen goods, I'm not certain there is any single thing in my home worth more than $25 to a burglar, other than the emergency cash. Rather than take the TV or any of the decade-old cap-rot Dell computers that have been re-capped, someone would be better off stealing all the meat out of the fridge, because at least they can eat that.
> The thing that saves most people is that there is really nothing worth stealing in their house
Agreed. I lived in a houseshare a couple of years ago where the housemates didn't want to chip in for contents insurance.
At first I was shocked, and thought about paying the whole house premium myself, but then I actually thought about it properly for the first time and realised that the sheer difficulty of removing and reselling my mostly quite heavy valuables (things like TV, drumkit, etc) and finding/sorting though even the smaller ones scattered around the place, would mean that any burglar that did get in would probably just decide to leave it. It wouldn't be worth the risk, effort, or arguably even their time.
I've not thought twice about contents insurance since. It's probably a product that makes no sense for a significant proportion of people (when you're renting and damage to furniture/appliances etc is covered by the landlord's insurance, of course!).
My family owns an abandoned house and it's been broken into like 10 times by thieves looking for stuff to steal. I believe they stole some guns and fireworks, and just trashed everything else.
If they successfully stole guns, then they were correct to break in. Guns are one of the most valuable items for burglars to steal. Why the hell were they left in an abandoned house?
Abandoned premises are a whole other thing. If the burglar has no worry that the occupants will return, they may try for more ambitious scores, such as removing the copper water pipes or condenser coils, or ripping up floors, walls, and ceilings looking for hidden caches.
Very interesting. I used to work with an older gentlemen who did RF comms in the military and back in early 2000s he used to tell me stories about his random RF hacking. One such story was around a garage door opener he modified with a potentiometer so he could test opening frequencies by rotating the dial. Obviously this wouldn't work for the "newer" style openers.
I've recently purchased a HackRF to start to learn about RF technologies in consumer grade "security" products like garage door openers, Z-Wave, wireless home security systems, etc. I've realized that after watching the first (very well done) video by Michael Ossman on HackRF that it's not going to be something easy to learn overnight.
While I'm sure this would be "easy" to do with HackRF given what I've read on Samy's site, does anyone have any input on how/why using this recycled hardware would be better in some regard?
Hi windexh8er, I choose this hardware because it's portable and convenient. It would technically be much easier to carry out this attack with something like rfcat via yardstick one, hackrf, etc, but I didn't want a USB based device and no need to build my own device when something existed with everything I needed! And did I mention it's pink?
Oh, don't get me wrong - I think it's awesome you're recycling and embrace pink. Thanks for the insight though and, well, I partially answered my question because the 8th video Ossmann actually walks through all of this on HackRF...
Can't one just sniff the code from the airwaves with a GNU radio RF scanner? Not that it is as cool as brute forcing it in 8 seconds but in someways it seems simpler and more universal.
Project idea: use a Raspberry Pi to control your garage door opener, and a battery powered microcontroller in a remote to use a challenge-response scheme to open a garage door.
I created a very similar device when I was 17. Back then though, most people with openers had analog remotes. This was one of the first times in my life I ever used (and subsequently purchased) a frequency counter. Oh, what excellent memories.
The "source code" of http://samy.pl is quite interesting
/*
No source for you!
*//
/.source.replace(/.{7}/g,function(w){document.write(String.fromCharCode(parseInt(w.replace(/ /g,'0').replace(/ /g,'1'),2)))});
There is a huge amount of whitespace is the page source. A mix of tabs and spaces. The page is encoded in that. Have a look in the inspector to see the decoded result. It's a bit like this: https://en.wikipedia.org/wiki/Whitespace_%28programming_lang...
Ah, looks like they have a regex that is just whitespace, get the source of it, and do some replacements to turn it into code. 7 bit binary, with spaces = 0 and tabs = 1
I had tried Samy's exact attack to reduce the brute-forcing time but it did not work at the time because I tried it before I discovered the code had to be sent 4 times consecutively (5 times makes it more reliable due to RF interferences). So I am not surprised to see Genie absent from the list of models Samy found vulnerable.
But I should try to find out the longest period of time during which these 4 repetitions of the code need to be sent. Maybe it does not have to be perfectly consecutive, but it could be 4 codes received within an interval of 200 ms or 1000 ms. If so it might still be possible to build a modified De Bruijn sequence that repeats codes 4 times while being only 4 times longer.
By the way it is very surprising a description of the 12-bit Genie protocol does not appear to exist online. These remotes are so easy to reverse engineer, so common (Genie is in the top 3 or top 4 most common openers), and so old (the protocol has existed since 1985), you would think there would be information about it online, but nope.
PS: I wonder if there could be commercial interest in cryptographically secure garage door openers? A $0.50 ARM Cortex-M0 MCU is all you need to implement a HOTP based on HMAC-SHA1. Then a simple learning/pairing system writing the key in EEPROM can even sustain the battery being removed from the remote. But there is probably no interest... which is why most remotes are insecure even the "rolling code" ones.
(Edited to clarify some tech details.)