A Raspberry Pi dashcam with two cameras and a GPS

http://pidashcam.blogspot.com

by aithoughts • 10 years ago

167 85 10 years ago

pidashcam.blogspot.com

jakobdabo2• 10 years ago

Thanks for sharing.

Little bit off-topic question for HN: is there any encrypted Linux filesystem which can be mounted in write-only mode using only the public key, and read-write mode using the private/public key-pair?

I think that kind of filesystems would be very useful for dashcams and security cameras owners for their privacy.

pmontra• 10 years ago

I found this http://www.arthy.org/wocfs/ I have no idea if it really works. If you give it a try would you mind letting me know?

robryk• 10 years ago

It'd be hard to imagine how that should work on filesystem level (if I can't read contents of any directory, how do I figure out which directory do I add a newly created file to?).

OTOH, on the file contents level this seems very much doable. Sadly, I am unaware of any general purpose implementation of such a thing (encfs doesn't do anything of this kind).

tw04• 10 years ago

You create a new directory on start that is based on the date/time - which you know will always be unique.

cnvogel2• 10 years ago

For the pretty limited usecase of a "record only" dashcam, you might consider recording in chunks.

Create an ephemeral key for a symmetric encryption in advance, encrypt this ephemeral key with the public-key method of your choice and store somewhere. Then encrypt one minute of recording using this ephemeral key. I don't know if gnupg is performing good enough on all architectures, but in principle it can handle everything in one go, and it works exactly as described just above.

      ~ dd if=/dev/zero bs=1M count=50 | gpg -e -r 0x6AC3E4EC >encrypted.dat
    50+0 records in
    50+0 records out
    52428800 bytes (52 MB, 50 MiB) copied, 0.486881 s, 108 MB/s

    (Intel(R) Core(TM) i5 CPU M 450  @ 2.40GHz)

If you use mpeg transport streams, you can even cut at arbitrary positions (to make, say, each file exactly 50 MiB large). When you play back, decoders will catch up as soon as they find the proper markers. So your encryption pipeline doesn't even have to know much about video...

cnvogel2• 10 years ago

Just pondered... there might be everything already be installed in a typical linux system, "split" does the right thing and can pipe into a command. Probably not the most efficient (making several copies of the data), but certainly enough for a proof-of-concept.

    $ dd if=/dev/urandom bs=1M | \
        split -b5000000 -d -a4  --verbose \
        --filter="gpg -e -r 0x6AC3E4EC >\$FILE" \
        - recording_ 
    executing with FILE=recording_0000
    executing with FILE=recording_0001
    executing with FILE=recording_0002
    (...)

• -b500000 split at 50 megabyte input file size.

• -d decimal suffixes (0001, ... else aa..az..zz)

• -a4 : suffixes of length 4 (0000)

• --filter="" : filter through pgp, intended output file is in variable $FILE

• - : read stdin

• recording_ : prefix output files with this string

    $ file *recor*
    recording_0000: PGP RSA encrypted session key - keyid: 8F74FAFF 29C8C7C2 RSA (Encrypt or Sign) 2048b .
    recording_0001: PGP RSA encrypted session key - keyid: 8F74FAFF 29C8C7C2 RSA (Encrypt or Sign) 2048b .
    recording_0002: PGP RSA encrypted session key - keyid: 8F74FAFF 29C8C7C2 RSA (Encrypt or Sign) 2048b .
    (....)

logicallee• 10 years ago

I read your requirements.

So, there's an analog loophole: in order to "write", the filesystem has to receive the data to be written - otherwise, it's untestable (if it doesn't get the data to be written it could write whatever it wants and pass all tests) which is a roundabout way of saying that if it doesn't get the data it can't possibly work. So it has to get the data. At that point it could be saved if the filesystem is modified (patched) to exfiltrate it. So we have to assume that you kind-of trust the filesystem not to be patched.

But if the filesystem is not modified, though, that means you're fine with the path that that data takes all the way until your filesystem writes it -- however, in this case your requirements are 100% met by encrypting to the public key and writing that out.

    #jakobdabo's requirements
    
    #include <pgp stuff>
    #include <filesystem stuff>
    
    public key = arg0
    private key = arg1
    
    read_file(filename){
      if (have_private_key)
          try decrypt(private_key, read(filenename))
            return result 
            except  "didn't work"
       else
           "I wasn't called with a private key."
      }
    
    write_file(filename, data)
        towrite = encrypt(filename, data) //encrypted metada inside
        try write towrite
             except "didn't work"

so this should meet all of your requirements. If you wanted the filesystem to do stuff like hide whether a file is even modified, hide timestamps, etc etc, those are almost impossible. Consider:

I want to determine whether anyone is accessing a server at the moment.

Server is idling, with sockets listening to answer web queries.

Suddenly 5,000 Reddit users show up and look through the site, generating lots of logs which nginx dutifully saves - only you're saving it in your encrypted filesystem.

Now.

How would you make it so that the fact that all of this traffic is being saved is hidden? The updates to the drive image would have to happen like clockwork regardless of what was happening. But this isn't a reasonable requirement, as the amount of entropy entering the drive is bigger while Reddit is hugging it than normal. You couldn't make it so that you are saving as much information as at top load. so what do you do? Reduce the top average to some level that you can continuously fabricate?

It doesn't make sense.

So you wouldn't hide whether any data was being saved by the dash-cam at all. but it's easy to save an encrypted version. the dash cam doesn't even need the private key.

but you do have to trust the software running on it. (for example to correctly do the encryption and not also write the underlying data somehow.)

Natanael_L• 10 years ago

Not quite the same thing, but forward secure sealing is relevant: https://lwn.net/Articles/512895/

You can always also use a smartcard type device to sign your files. Then a reboot (power cycle) will revoke signing capability until unlocked again.

Sanddancer• 10 years ago

You could always just pipe it through gpg or the like. Just encrypt using the public key, and you can't decrypt unless you have the private.

widdma2• 10 years ago

If you really wanted it to work like a file system, you could write a passthrough FUSE module which pipes files through GPG before writing to the underlying file system.

This seems like a good start: https://www.stavros.io/posts/python-fuse-filesystem/

ChuckMcM• 10 years ago

No need to do it at the filesystem level, just do it at the file level. You can encrypt using the public key in the dashcam, when you want to recover the video you bring the removable media to a system where you can use the private key to unlock it. Since there is often hardware support for AES you can use the public key to encrypt an AES key for the current segment, then when you get it home use the private key to recover the AES key and then use that to recover the video. The existence of the files is pretty obvious but they won't generally be decryptable.

jakobdabo2• 10 years ago

The advantage of doing this at the filesystem level is that you don't need to modify every piece of existing software which writes sensitive data (video/images/logs/etc.).

I'm thinking of an EncFS type stackable solution (as suggested by @robryk) based on FUSE because you could copy the encrypted files from the upper level filesystem when needed (without remounting the lower level filesystem in read-write mode) and examine them on an air-gapped computer which holds the private key.

The disadvantage of this type of stacked solution is that it wouldn't be possible to implement plausible deniability.

cr3ative• 10 years ago

This is neat, but I would worry that something which is intended to be "set and forget", without the usual screen, would fail silently - especially with such a custom build. How are you assuring that it is functional and recording?

pearjuice• 10 years ago

By verifying the contents of the hard drive once in a while?

ghaff• 10 years ago

If it's not done automatically it won't routinely happen though. I wonder about this with some sensors at home. Some of them routinely ping me with status but other commercial ones are pretty much fire and forget. I can certainly set calendar entries to run tests but you're better off with things are self-testing in some manner.

Nexxxeh• 10 years ago

If it's got wifi, you could check from your phone, or have it upload automatically from the garage (wifi range depending).

dogma113811• 10 years ago

Cool project, although I would not advise using dashcams if you are involved in an accident the police can subpoena the footage which could potentially be used against you (in both criminal and civil suits).

If you do run a dashcam I would suggest having one that does not record audio and only keeps the last 5-10min of footage on record because GL explaining to the cops why you have been driving like a jackass just before the accident even if it had nothing to do with it.

swsieber2• 10 years ago

Conversely, if you're a responsible driver then it prove that you are in the right.

fapjacks4• 10 years ago

Right. It's no accident (badum-psh!) that Russia and China are full of expensive cars with dashcams. Or even just regular cars with dashcams. The benefits far outweigh the penalties for the vast majority of dashcam users.

dogma113811• 10 years ago

I haven't met a single person who doesn't go above the speed limit (to a reasonable amount) or misses a give way or stop sign once in a while.

Zombieball2• 10 years ago

How long does it take for them to subpoena you? That is if I were in an accident, and they don't physically confiscate the memory drive, could you extract any video that supports your case and delete the rest before they request it?

I figure this happens with police dashcams and bodycams all the time.

dogma113811• 10 years ago

If the police is on the scene they don't even need a subpoena they can search the car and confiscate the memory card.

If you destroy the contents of the card it doesn't look good, that fact can be brought up against you (tampering with a car that was involved in an accident especially one with casualties could potentially be a crime on it's own).

If you present only the snippets that support your case the other party will petition the court to for you to present the unedited video if you cannot the entire thing will most likely be thrown out (the other side might be able to present the fact that you have attempted to present an edited video and have discarded the raw footage which will likely not fair well with a jury).

Not to mention that having the video it self could put you at risk of perjury or being found in contempt if you try to do anything after the fact.

gherkin02• 10 years ago

Wouldn't that be destruction of evidence? I don't think you're allowed to destroy things if you anticipate a subpoena.

m0nty• 10 years ago

why you have been driving like a jackass

Or just don't drive like a jackass. It's a serious business, take it seriously.

CamperBob2• 10 years ago

"What dashcam, Officer? Oh, that? It hasn't worked for weeks."

dogma113811• 10 years ago

Lying to a police officer is a crime in most jurisdictions, it's called making a false statement.

danielweber• 10 years ago

Some people keep records because they honestly believe they are doing things properly and want to be able to prove it.

placeybordeaux• 10 years ago

Is there well documented cases of this?

marincounty• 10 years ago

This is a good idea. The costs from getting a pulled over for no reason is a big deal. I gave been pulled over for no reason, so many times, you'd think I wasn't in America.

I bought two $15 Chinese dash cams. The same ones that are being peddled for 40 bucks plus S&H on t.v.

I bought the second one just in case the first one goes down.

I haven't been pulled over since.

fapjacks4• 10 years ago

So you intentionally mount these things front/rear and plainly visible to police? Interesting. Also, what model camera did you buy?

j_s• 10 years ago

I'm interested in this too! I bookmarked the $20 Go-Pro-ish substitution recommended here, which was explained to be counterfeit the next day:

https://news.ycombinator.com/item?id=10898640

nommm-nommm5• 10 years ago

Not GP but I own this camera http://ebay.com/itm/310752336819?_mwBanner=1

kyberias• 10 years ago

I haven't been pulled over since.

How many times did you get pulled over before the cameras and over what time period? And how long have the cameras been installed?

tajen• 10 years ago

Side question: Is it customary to drive across the dotted lane?

dsr_• 10 years ago

A dashed lane marking means that both sides may temporarily use the other lane to pass -- provided that they can see it will be safe. A solid center line means you cannot do that. A double line with one side solid and one side dashed means that the dashed side may attempt to pass, not the solid side.

All of these things become more clear once you realize they are primarily about sight-lines.

ars3• 10 years ago

Yes, you can change lanes across a dotted line as you like. You do have to signal first though.

What does a dotted line mean in your country?

arthulia• 10 years ago

Did you watch the video in the article? He is driving with the middle of the car over the dotted line. If I had to guess, I'd say it's a two-way one-lane road with bike-lanes on either side that you can enter when cars are coming towards you.

0942v8653• 10 years ago

Link to "original" video if you have Flash disabled: https://www.youtube.com/watch?v=hCbZsu68zZU

blisterpeanuts• 10 years ago

Maybe I missed it in the instructions, but how does the system handle the shutdowns? Does he manually shut it off each time, before USB power is turned off, or does it just handle the power cut-off gracefully? I worry that the file system will get corrupted after a while.

There was some discussion about this on a pi board a while back; it seems that the only safe way to handle power-off is to (1) have a battery on the pi, and (2) catch the USB power-off signal and then shutdown gracefully.

At least, that's how the Chinese dash cams seem to work. They all have rudimentary batteries that last about one minute unplugged from the power outlet.

caffinatedmonk• 10 years ago

He wrote about handling shutdowns in another post on his blog.[1]

For the automatic shutdown I have used a 12V programmable timer in combination with an optocoupler.
When the car is powered the the timer gets triggered and is starting the power supply for the Raspberry pi, Dashcam pi will get started and will do its job. When the car is turned off the optocoupler triggers the GPIO pin of the raspberry and starts a shutdown. After 15 seconds the timer is shutting down and the raspberry pi is powerless.

1: http://pidashcam.blogspot.com/2016/03/cheap-solution-for-aut...

Animats• 10 years ago

If you're going to have multiple cameras, the next step is to combine them into one spherical image. Fujitsu has been doing this since 2010.[1] With four cameras, you can get the full vehicle perimeter. Other companies now offer such a capability.[2]

[1] http://www.fujitsu.com/us/products/devices/semiconductor/gdc... [2] http://www.fujitsu.com/us/products/devices/semiconductor/gdc...

ps4fanboy• 10 years ago

I would love to see a camera like the Dyson 360, that you mount on the top of your car.

http://o.aolcdn.com/hss/storage/midas/93697564cc7197a3e35979...

I guess it probably wouldnt work though as close objects would be obstructed.

teekert2• 10 years ago

Very nice! Love it that he uses Arch, I also used to use Arch for everything, and I also run a RPi tutorials website.

I switched though, because the only questions I'd get was of people using my commands on Raspbian and getting confused. I think the RPi audience is full of beginners that don't understand the difference between distro's and the kernel. Of course one should do as one pleases and Arch is the nicest distro if you known what you are doing, imho.

undersuit2• 10 years ago

I'm a solid Debian user but I still keep the Arch wiki around since so much of the information is completely transferable.

I switched though, because the only questions I'd get was of people using my commands on Raspbian and getting confused.

Not to attack your blog but was everything that Arch specific?

teekert2• 10 years ago

Well, there's Pacman, Yaourt, no sudo by default, no Python-GPIO package by default, no Gui by default, no raspi-config... etc.

mschuster91• 10 years ago

If possible, I'd use two flash drives, mirrored with soft-raid, for storage. One clearly visible in the dashcam, the other hidden somewhere deeeep inside the car with an USB extender.

Why? Because if a cop/other driver ever gets mad at you and forces you to hand over the flash drive, you still have a copy.

Also, I'd add two microphones to the project, one for exterior sound, one for interior (e.g. to prove what exactly has been said, or in case of a crash if other drivers have honked, or if an ambulance had its sirens on).

And, I wouldn't use a Pi, but rather something supporting SATA, because USB flash drives tend to have low lifecycles when constantly overwritten.

codeulike• 10 years ago

My raspberry pi is great fun but a bit prone to failing randomly and very sensitive to input power levels, not sure I'd trust it if it was hooked up to car electrics.

Grishnakh• 10 years ago

That's not a problem. It isn't that hard to design (or buy) a circuit to provide clean power from an automotive power source. The "carPC" community has been doing this for ages.

johnflan• 10 years ago

I have played around with this a little, using the camera pi module gives good results, but means you must mount the pi close to the camera. I wanted to use USB cameras but the USB bus on the pi is too slow. From a single USB webcam I was getting around 15fps. The newer pi's may have a faster USB bus.

otterpro2• 10 years ago

This is a really cool project, and I'm always thinking about doing something similar with RPi or other small computer. In the past, I had built my own x86-based CarPC for music/media/GPS/automation/etc.

However, the rise of dash cams are better solution for video as they are much cheaper, easier to install and run, and video is much higher quality. The cheap $45 dashcam has 1080p with 30fps, no need to buy 12v relay timer and deal with other power issues. Also the video on dashcams outperform the webcam attached to the RPi due to RPi's slow USB2 (we're talking 15fps at best).

For more complete and capable product, I'd suggest using something with USB 3.0 port, or possibly a used laptop, which provides enough processing power to record multiple videos at higher quality, and at the same time, has built-in battery, provide power management (using serial port/other hack to handle automatic shutdown and WOL for reboot).

Note: A lot of the functionality of CarPC has been deprecated due to mobile device/phone/tablets, but it's still fun to have a PC running in a car.

otterpro2• 10 years ago

Actually, I think if you have all the parts already (i.e. RPi, webcams), this makes a lot of sense. Creating a Frankenstein system out of existing components would be interesting, and cost would be zero.

A Raspberry Pi dashcam with two cameras and a GPS

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