HOWTO anonymize your digital photos
Instructables has just posted the latest installment in its ongoing series of HOWTOs inspired by my young adult novel Little Brother, which tells the story of a teen underground that uses technology to fight back against surveillance and control.
This week's HOWTO is "Avoiding Camera Noise Signatures" -- AKA, anonymizing your photos before you post them online:
Link, Link to feed of Little Brother InstructablesIf you take enough images with your digital camera, they can all be compared together and a unique signature can be determined. This means that even when you think that you are posting a photo anonymously to the internet, you are actually providing clues for the government to better tell who you are. The larger the sample size of images they have, the easier it is them to track down images coming from the same camera. Once they know all the images are coming from the same camera, all they then have to do is find that camera and take a picture to confirm it beyond a reasonable doubt.
It is important to remove this noise signature so that you cannot be tracked down. I cannot guarantee any of these methods will work beyond the shadow of a doubt because the woman doing research for the government on how to find the signature is very good. I can only promise that this will make their work more difficult.
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Who is actually this paranoid?
Terrorists are.
One good way to see the thermal noise of your camera (and you can also use this as part of a process to remove it via photoshop) is take a picture with the lens cap on.
I can't remember exactly how I used to do it, but I know I would set up a night shot on a tripod, then take a shot with the cap on, then without moving the camera at all, I'd take another shot of the scene. Then later in photoshop I would layer the two pictures and remove the thermal noise with a process I can't remember now.
I'm sure the info is still out there on google somewhere:
http://www.google.com/search?hl=en&q=removing+thermal+noise+camera+lens+cap&btnG=Google+Search
"Terrorists are"...... right, because when they post their vacation snapshots they really don't want the government to trace them back to them so they can be apprehended for the inappropriate wearing of a speedo... Scheesh - there is paranoid and funny paranoid. This leaps into I-really-need-to-get-a-life paranoid. Trust me, no one cares about you this much.
#1 posted by Tecumseh:
Uh, people that this means life or death for (you have heard of oppressive modern regimes that kill dissenters, correct?)... or people in the U.S. that are involved in patriotic actions of dissent that don't want their organizations and/or life ruined because their right to privacy is trampled on (and taken advantage of).
Uh, you do know about things like this, right? (tip of the iceberg)
http://www.crooksandliars.com/2008/04/30/don-siegelman-speaks-with-thom-hartmann/
http://www.democracynow.org/2008/4/14/black_ops_on_green_groups_private
http://www.google.com/search?num=100&hl=en&safe=off&q=%22activist+killed%22&btnG=Search
Go back to sleep, Tecumse.
Interesting. Reminds me of my undergrad research astronomy research. Astronomers have to deal with this all the time, and there is existing software and procedures to handle it in a mostly-automated sort of way. Google for flat fields, dark frames, and bias frames to get the gory details.
Surely it would be possible to use software to add noise to your photos, based on a random number generator. People who work on open-source image manipulation programs could add this feature.
#3:
My current digital camera (a Panasonic Lumix DMZ-TZ3) has a feature where if you take a picture with an exposure longer than 1 second, it automatically takes a second picture of the same exposure length with the shutter closed and subtracts the dark frame automatically. My old Cannon SD100 did the same thing.
Step 0. Write your own software to do all this, or use open source software and audit every line of code in it.
If you're using closed source software you have no way to tell if it is, say, encrypting your name with the NSAs public key and watermarking it into every image you save. That may seem paranoid, but color laser printers have done it for years -- why should you assume software doesn't?
Great Post! For a second I had almost forgot that Cory's book was relative to everything else. Phew!
What is an example of some picture that would warrant this kind of security measure?
Sheesh, can't believe no one thought of just using a different camera for each picture.
I understand that these sorts of measures are useful to some living under oppressive regimes, but the manner in which the post was written made it seem like these were precautions anyone would (and should) be following, as if "they" are always out to get us.
About Photo anonymity,
In VISTA (don't laugh at me please) when i'm looking in a folder using explorer, a glitch
happens with "fossilized" thumbnails of image files.
It tends to happen in folders containing more than 100 image files.
The thumbnails initially appear as the ORIGINAL image but after a second, the thumbs seem to auto refresh to show the current image state.
For instance, if there were shots you cropped yourself out of,
Anyone with vista can see YOU in thumbnails for a second before the thumb refreshes to the current
image state...
it seems to be something with the structure of the image files (and NOT VISTA stored back up
tempfiles) since it seems to happen equally with files that are 7 years old, and have been bounced back and forth from pc to mac and back again.
Does anyone out there know anything about this?
@Nehpetse
When you are looking at thumbnails in Vista (and other versions of windows), the images that you're looking at aren't the actual image files. They're actually saved in a file called thumbs.db.
If you go into the folder options, and set it to show hidden files, you'll see it.
Then when you update the image, thumbs.db gets updated. It's a lot faster than having vista open every file and create a thumbnail each time you open the folder.
Tecumseh #13 -- Even if the country you're living in now is free and open, it may not always stay that way, or you may not be living there forever.
#11 posted by Jeff , May 1, 2008 9:59 AM
Of many examples... how about for posting photos of authority figures doing illegal/unethical acts that you want to expose? The authority figures would just love to be able to find out who you are, huh?
I'm surprised in this day and age there are so many within this thread wondering why anyone would want to be anonymous. In the meantime, I sure don't see a whole lot of your first and last names being used here for screenames here.
What have you got to hide? Is everyone here a... terrorist?
LOL, gawd... America, home of the bra... chicken.
Sam
I know this.
I always have all hidden files set to be visible, and have repeatedly deleted thumbs.db
Explorer is actually MORE likely to briefly flash the original pre-edited image when i have deleted ALL stored thumbs and Explorer has to create all new thumbs.
When you live in prison, you take precautions to stay out of trouble. And you do so all the time. The country's police, intelligence forces, and armed services are now our prison guards, and they can invent reasons to take out anyone they don't like. Ask that guy who was taken out by the Secret Service acting through local cops to jail for a few day of his life for walking up to Cheney and telling him off. Or that guy in New Orleans who told Cheney to Cheney himself after the VP shut down his street to stage a media event after the flood. He was arrested , too. And the NYC protests with the cops lying about lawbreaking to round up and jail anti-Republican protestors. How about Chicago, where Daley scooped up everyone on the street during our big war protest and hauled them off to jail, for the crime of being anti-war. How many others have gone to prison without anyone noticing, for the simple reason that they annoyed the wardens? And we assume prosecutions are not political - but remember weapons inspector Scott Ritter, who after popping up on TV saying Bush was lying about the WMDs, was hauled off on kiddie porn charges -- and was later released, charges dropped. Obviously was monitored and flimsy "evidence" provided. What if the shadowy men who staged that takedown had added watermarks to a kid porn pic indicating that Ritter had taken the shot? How would you KNOW? He's simply be in prison for twenty, and we'd be making Ritter/Girl Scout jokes for a hundred years. And keep in mind such a thing doesn't have to happen -- they can keep us in line knowing that we never can tell if they will choose, at some time unknown, to manufacture such "evidence" to nail their Nixonian enemy list. I especially point to the GPS trackers in our phones. They are accepted as direct evidence in court. What if they simply alter the text, and place you in a crime scene of their choosing? How would you know, how could you prove it? Who would even care to hear you protest? Our wardens have already demonstrated that they were willing to frame Ritter; it was a shot across everyone's bow. We know they can fabricate tech "evidence". So we are oh-so-careful not to offend the creatures. Police states are free only for the police and their bosses. Once they are in place, they are impossible, short of societal/economic collapse/war, to remove.
I note the "DC Madam" has "committed suicide"
This is an interesting field. For example someone could substract the noise signature of their own camera, and add the noise signature of another camera, which they can obtain for example from a sample of photos from flickr.
Manipulations at the pixel level are not that esoteric, they can be done in Visual basic for example.
I couldn't' think of a reason why someone would do this till I read the comments. If I was someone in china documenting police abuse this trick may come in handy.
#1 posted by Tecumseh , May 1, 2008 7:57 AM
Cannabis growers are. They often exchange pictures and information over the net in order to better their product or organize transactions.
Again, who will guard the guards?
If I was someone in china documenting police abuse this trick may come in handy.
This is rather interesting to know in the modern digital times in which we live: the source of the image being determinable would in many cases be advantageous. With digital media, there's typically no degradation present in copies made from the original. The camera then becomes the "dongle" in cases where you need to establish claims of right with regards to the source media.
Presumably this applies to other A->D converters as well: mics, environmental sensors, etc.
"Who is actually this paranoid?"
Normal people get a little upset when the odds of them being removed from their home and senselessly tortured rises above zero.
how can extract the camera signature fom my target's camera and then upload kiddie porn to the web that bears the target's signature?
So I am wondering about solutions to this. What if you, say, took your pics to photoshop, and added a .1 or something smart blur. Think that would solve it? Get rid of the nasty little pixel sigs?
sorry Catbeller, just read your post properly. You have the correct sort of mind.
Another option is to have a camera specifically for nefarious use. If the only samples of the camera's noise signature investigators have is from images of your selection, then the best they can do is correlate them to others you've selected. Just have a different camera for Facebook and snapshots and such and treat the "guilty" camera like a "hot" item.
Don't steganography tools already do this? Seems like you could just generate enough random bits, and set whatever software to replace all the however many least-significant bits with it.
Did anyone follow the link to Jessica Fridrich's website? She's the specialist conducting the noise signature research.
Turns out, besides arming the machine to hunt down freedom-lovin' photo-bloggers, she's a crazy fast Rubik's Cuber achieving up to TEN MOVES A SECOND ! !
Check out this video of her solving the cube in 14.33 seconds, and read about the multiple conditional algorithms (up to 100) she uses in her head, to achieve it.
I think we're gonna need more that a little bit of 'add noise' to beat this one.. Mental.
Seems to me the people happiest to use this sort of thing are pedophiles. Those who are oppressed often (not always, as you oppressed Americans would know) have no access to places like Boing Boing to tell them what to do.
That said, I wouldn't censor this info at all. Just need to add that proviso.
D
Derryl Murphy sez - "Seems to me the people happiest to use this sort of thing are pedophiles."
One simple question Derryl, WTF are you talking about? Someone who posts a photo to the internet, and doesn't want to be identified by the government or some "security service" is most likely a pedophile? I hope you are kidding.
#32
What does that even mean?
I have a modest proposal. Anyone who ever uses the word 'pedophile' online goes on The List and loses their computer for life. Think of the children. Why can't we all just think of the children.
I'm amazed that people still need to ask "Why on earth would you need privacy, unless you're a terrorist or a paedophile"? Perhaps you've never met any journalists, lawyers, law enforcement agents, private investigators, protesters, human rights activists or the like.
I consider this sort of thing valuable information.
I'd consider removing the EXIF data (which stores camera model, date, time, lens and exposure settings) to be even more important.
I just use someone else's camera
This instructable is mostly nonsense.
It does suggest removing the EXIF tags*, which (as Symphonix pointed out above) would be enough for the vast majority of cases.
The paper that this is based on suggests that cropping, resizing, filtering, lossy compression and/or gamma correction will not prevent identification.
It does specify 'no geometrical transformations', though, so a rotation of a few degrees (or any non-uniform geometrical transform) may be enough to beat it.
Adding per-pixel random noise will only prevent identification where the new noise overwhelms the old noise- it would be hard to know how much would be enough...
This all relates to attempting to match images by camera- matching images to a known camera (e.g. where forensics have a suspect's camera and want to determine if images originated from it) is a little easier, and so would be harder to beat.
*When I post images to the web, I often use a python script to resize them, and generate thumbnails- using wxImage for the conversion incidentally discards all the EXIF data, and other jpeg comments.
"Trust me, no one cares about you this much."
Considering there's a research group developing this technology for the US government... SOMEBODY cares.
I'm assuming what #32 meant was that persons performing illegal activity that involve the sharing of digital photographs would be pleased to know how to do this.
I believe they then thought of the different types of illegal activity taking place using digital photographs.
It is very easy for me to think warmly about the possiblity of activists, dissenters and journalists using this to protect themselves.
It is disturbing to think of pedophiles using this information to avoid discovery.
duh.
info on JFIF thumbnail structure
ImageMagick or something can probably strip the thumbnails en masse if you want.
Jake @ 33, I didn't say "most likely to use," did I? Practice those close reading skills and look at the words. Me, I'm casting my memory back to that asshole who posted pix on the web that they were able to unscramble:
http://www.usatoday.com/news/world/2007-10-15-1601556333_x.htm
Certainly other people would have use for this. But for you and Arkizzle @ 34, it means just what it says. Any technology that helps law-abiding citizens avoid detection will also help law breakers. And therefore it's worth talking about whether or not something can be done, what the risks are, and whether or not we actually should do something. Something that is good for pedophiles is probably worth a closer look than certain other technologies.
D
Don't beleive the bunk!
JPEG Compression adds enough artifacts to remove any noise with even minor compression.
Next, DSLR's can have dust and it can change often.
Lastly, Don't keep your EXIF Data. Create a new blank photo, copy the old image and past into the new. Use free web serviecs like Picnic to edit the image, resize, crop, and compress.
Anyone who shoots RAW from the same camera and posts the full resolution images while fearing being tracked is an idiot.
Reducto ad Pedophilium?
Anyway, the issue with digital anything is the ability to investigate retroactively.
How many execs have been busted for years-old emails they thought were securely deleted. In those cases actual crimes were being committed, but the point is that we're not sure what is going to be made a crime some day in the future, and how much due process or other Constitutional protections will still be in place at that point (like the double-jeopardy clause, as one relevant example).
Photoshop's "Save for Web" removes the EXIF data while compressing the crap out of your image.
I'm a little curious as to whom has access to this magic tracking ability. Despite what you see on TV, most law enforcement agencies couldn't find "Plans To Destroy The World.doc" in your average crim's My Documents folder. Presumably if you are suspected of being Extra Bad you'll get real technicians on your ass, though.
#43, Drachezan:
Read the paper; the authors used jpeg files to match pictures by camera.
Jpeg compression is functionally identical to resizing the image in this case- the overall pattern of sensor response is retained, though with less precision.
Derryl @42
Actually, I genuinely couldn't see what your sentence was trying to convey until MissLauraLee pointed it out. It was either the way u wrote it or the way I read it.. meh.
However, I would put on a not-too-shakey bet, that people who own digital cameras, and have the opportunity to post their photos to the internet, and be analysed and tracked by a government, probably also have access to the 'reading' section of the internet, and may even have the good taste to read BB and Instructables.
Do I think we should restrict our own knowledge because Teh Pedoz'll use it to their own nefarious ends? No. I suspect there are FAR more politically endangered people in the world than pedo' endangered ones.
The people paying for this research are the government, the airforce and the military. Not the anti-NAMBLA groups, not parents of harmed children.
Do you think the military will share such a nice toy as this? I doubt it.
Here's my favorite pedophile story about a pediatrician whose home was vandalized because the local peasantry couldn't tell the difference between a baby doctor and a baby diddler.
#43, Arkizzle:
Read the paper; the 'nice toy' has already been shared in this publication. Anyone who can understand the maths can implement it themselves. The authors suggest it would be useful in court cases, in particular child porn, movie piracy, and insurance claims.
#49
dammit! :)
Also: nice that we have the specs to defeat it.