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Signs that can reveal a fake photo (2017)

bbc.com

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Re: Signs that can reveal a fake photo (2017)

#31

Post by mindslight »

hdm41bc wrote: post #14

Is this a solvable problem by requiring camera manufacturers cryptographically sign photos and videos created on those devices? If that’s in place then it seems like it could be the basis for chain of custody of journalistic images backed by a blockchain. This seems like the only viable solution to me since any AI powered solution would just be a cat and mouse game.

No. "Trusted" hardware merely creates the illusion of a secure system, while allowing those with the resources to defeat it anyway. First, there would be 20 years of bugs after having to root your camera became a thing. Two, unless the sensor modules themselves are made into trusted components, it would be relatively easy to wire up a mock sensor to the "secure" processor. And three, camera makers would eventually be pressured to undermine the system's security invariants, ala Apple.

Re: Signs that can reveal a fake photo (2017)

#32

Post by z5h »

jobigoud wrote: post #30
z5h wrote: post #28

I tried to prove that crops which do not preserve photographic centre are detectable https://physics.stackexchange.com/a/367981/3194 This was after photographers seemed to not believe this was the case https://photo.stackexchange.com/q/86550/45128 In any case, detecting cropped photos could be a way to detect that something has been intentionally omitted after the fact.

But cameras aren't perfect pinholes though. The center of the sensor and the optical axis of the lens are already not perfectly aligned, and the sensor is not necessarily perpendicular to the lens barrel. These distortions might be larger than any change of size due to an object being in the periphery of the field of view, especially for longer focal length where the rays are more parallel.

Correct. So, in theory it works and in practice it works with limitations. You could probably create a lens/camera calibration profile that could take the practical use further.

Re: Signs that can reveal a fake photo (2017)

#33

Post by MayeulC »

hdm41bc wrote: post #14

Is this a solvable problem by requiring camera manufacturers cryptographically sign photos and videos created on those devices? If that’s in place then it seems like it could be the basis for chain of custody of journalistic images backed by a blockchain. This seems like the only viable solution to me since any AI powered solution would just be a cat and mouse game.

I was speaking with someone from the military. It seems that's more or less required in some cases for interrogations, taking pictures of proofs, etc. With time-stamping and GPS coordinates using purpose-built cameras.

I can easily imagine the camera digitally signing pictures and asking for notarization. But there will always be an analog hole -- and the first faked pictures weren't altered after shooting, the scene was.

I'm all for fakes being widespread. It makes people more critical of what they see, and protects them against the few that had this capability before.

Re: Signs that can reveal a fake photo (2017)

#34

Post by grumbel »

kc0bfv wrote: post #16
hdm41bc wrote: post #14

Is this a solvable problem by requiring camera manufacturers cryptographically sign photos and videos created on those devices? If that’s in place then it seems like it could be the basis for chain of custody of journalistic images backed by a blockchain. This seems like the only viable solution to me since any AI powered solution would just be a cat and mouse game.

In this scenario, it would almost certainly have to be that manufacturers would have to build cameras that cryptographically sign the images and videos. The cameras would have to be able to have that ability, install of the manufacturers doing the signing. And then what would the Blockchain provide in this case? A chain of cryptographically signed certificates back to a manufacturer is basically the same system we us…

> And then what would the Blockchain provide in this case?

The main thing a blockchain provides is a cryptographically secured logbook of history. It doesn't guarantee you that the entries in the logbook are true, but it gets a lot harder to fake history when you can't go back to change your story. You have to fake it right when you claim it happened and hope that nobody else records anything in the logbook that conflicts with your story.

Re: Signs that can reveal a fake photo (2017)

#35

Post by someguyorother »

hdm41bc wrote: post #21
kc0bfv wrote: post #16

Earlier quoted context omitted.

In this scenario, it would almost certainly have to be that manufacturers would have to build cameras that cryptographically sign the images and videos. The cameras would have to be able to have that ability, install of the manufacturers doing the signing. And then what would the Blockchain provide in this case? A chain of cryptographically signed certificates back to a manufacturer is basically the same system we us…

The way I thought that the blockchain would be employed is to use it to track transformations of the image. Post-processing, adding captions, and what not. This would provide an audit trail of changes to the original source image. If, in fact, we can’t reliably sign the source image as authentic, then the rest of the system falls apart. It seems like this is the crux of the problem.

That seems to be a DRM problem. Let's say that you want the camera to track all modifications of the picture. Then, analogous to DRM, there's nothing stopping the forger from just replacing the CCD array on the camera with a wire connected to a computer running GIMP.

To patch the "digital hole", it would be necessary to make the camera tamperproof, or force GIMP to run under a trusted enclave that won't do transformations without a live internet connection, or create an untamperable watermark system to place the transform metadata in the picture itself.

These are all attempted solutions to the DRM problem. And since DRM doesn't work, nor would this, I don't think.

Re: Signs that can reveal a fake photo (2017)

#36

Post by kc0bfv »

grumbel wrote: post #34
kc0bfv wrote: post #16

Earlier quoted context omitted.

In this scenario, it would almost certainly have to be that manufacturers would have to build cameras that cryptographically sign the images and videos. The cameras would have to be able to have that ability, install of the manufacturers doing the signing. And then what would the Blockchain provide in this case? A chain of cryptographically signed certificates back to a manufacturer is basically the same system we us…

> And then what would the Blockchain provide in this case? The main thing a blockchain provides is a cryptographically secured logbook of history. It doesn't guarantee you that the entries in the logbook are true, but it gets a lot harder to fake history when you can't go back to change your story. You have to fake it right when you claim it happened and hope that nobody else records anything in the logbook that conf…

I can see how then a journalist source could use this to help prove their integrity. And I like that as a solution for that...

But - I don't really see that as the issue today. Those outlets that are interested in lying don't have to participate in this Blockchain chain of proof system. The malicious entities like political groups cited in the article definitely don't have to participate. It's still really on the viewer/spreader of the fake images/misinformation to verify the images, and to only rely on verifiable images. But I think a system like that would leave out most of the population who simply don't care.

Perhaps my worry about leaving out that chunk of population means this problem is unsolvable - and therefore my point is unfair. But I do think we need some solutions that are practical for widespread acceptance and use. If I can't imagine my parents (who are tech literate) would participate, and can't imagine some of my non-nerd friends wanting to participate, I don't think it solves the problems I'd like systems like this to solve.

Re: Signs that can reveal a fake photo (2017)

#37

Post by kc0bfv »

kkielhofner wrote: post #27
kc0bfv wrote: post #16

Earlier quoted context omitted.

In this scenario, it would almost certainly have to be that manufacturers would have to build cameras that cryptographically sign the images and videos. The cameras would have to be able to have that ability, install of the manufacturers doing the signing. And then what would the Blockchain provide in this case? A chain of cryptographically signed certificates back to a manufacturer is basically the same system we us…

The problem with using certificates is any media signed by a party (by nature) traces directly back to that source/certificate. With a certificate-based approach I can imagine something like Shodan meets Google Image Search being used to make it easier to source media for the purposes of enhancing training for an ML model. Needless to say I have serious concerns about this approach. This is why our approach only embe…

Ok - I like this for some use cases. To restate my understanding so you can tell me I'm wrong if I am:

I think that it's still the user's job to make sure that they are skeptical of the provenance of any photos that claim to be from, say, the NY Times, that are not viewed in the NYT's viewer (if they were using your system). And then, they should still trust the image only as far as they trust the NYT. But if they're viewing the image the "right" way they can generally believe it's what the NYT intended to put out.

And perhaps, over time, user behavior would adapt to fit that method of media usage, and it would be commonplace.

I am skeptical that that "over time" will come to pass. And I think that users will not be apply appropriate skepticism or verification to images that fit their presuppositions. And I think malicious players (like some mentioned in the article) will attempt to build and propagate user behavior that goes around this system (sharing media on platforms that don't use the client, for instance).

And I guess making that broad set of problems harder or impossible is really what I'd like to solve. I can see how your startup makes good behavior possible, and I guess that's a good first step and good business case.

Re: Signs that can reveal a fake photo (2017)

#38

Post by kkielhofner »

kc0bfv wrote: post #37
kkielhofner wrote: post #27

Earlier quoted context omitted.

The problem with using certificates is any media signed by a party (by nature) traces directly back to that source/certificate. With a certificate-based approach I can imagine something like Shodan meets Google Image Search being used to make it easier to source media for the purposes of enhancing training for an ML model. Needless to say I have serious concerns about this approach. This is why our approach only embe…

Ok - I like this for some use cases. To restate my understanding so you can tell me I'm wrong if I am: I think that it's still the user's job to make sure that they are skeptical of the provenance of any photos that claim to be from, say, the NY Times, that are not viewed in the NYT's viewer (if they were using your system). And then, they should still trust the image only as far as they trust the NYT. But if they're…

It's probably best for me to provide an example. We create three URLs for each media asset. For [1], [2], and [3] you can click our icon in the top right corner:

- A link to the asset itself (just the JPEG or whatever with embedded ID) [0]

- A link to a preview with twitter card, facebook open graph, etc support suitable for sharing (and re-sharing) on social media [1]

- A link to an iframe embed for use wherever else [2]

For an asset where the user has configured the metadata to be hidden our verification API doesn't return anything other than the checksum to validate against [3].

Users can update the returned metadata at any time or hiding of the extended metadata and it's updated dynamically and instantly - everywhere. So this way producers and consumers of content don't need to have a dedicated consumption implementation (but it could certainly be branded or white labeled to the content producer). Currently the client is just our javascript but we're working on mobile and browser extensions that can run anywhere against the raw asset link provided in [0].

[0] https://share.tovera.com/assets/c65b0658ab6e4d89963b1e0a319a...

[1] https://share.tovera.com/preview/c65b0658ab6e4d89963b1e0a319...

[2] https://share.tovera.com/embed/c65b0658ab6e4d89963b1e0a319a1...

[3] https://share.tovera.com/preview/e51de3d34bfe47d7bc25fb8f252...

Re: Signs that can reveal a fake photo (2017)

#39

Post by hdm41bc »

kc0bfv wrote: post #36
grumbel wrote: post #34

Earlier quoted context omitted.

> And then what would the Blockchain provide in this case? The main thing a blockchain provides is a cryptographically secured logbook of history. It doesn't guarantee you that the entries in the logbook are true, but it gets a lot harder to fake history when you can't go back to change your story. You have to fake it right when you claim it happened and hope that nobody else records anything in the logbook that conf…

I can see how then a journalist source could use this to help prove their integrity. And I like that as a solution for that... But - I don't really see that as the issue today. Those outlets that are interested in lying don't have to participate in this Blockchain chain of proof system. The malicious entities like political groups cited in the article definitely don't have to participate. It's still really on the vie…

I don’t think most people need to adopt this on their cameras for it to work. My perspective here is that journalistic sources that want to be trusted could employ this system. Along with signing the media and the blockchain, a system would need to be built to simply show the change log and history of a photo from the source. These journalism websites could just link out to it to demonstrate their veracity.

Once that’s adopted by the NYTs, WSJs, BBCs of the world, I’m hoping there would be critical mass to pressure more and more journalistic sources to adopt this standard. Eventually, any credible journalism would be on this technology and any outlet that doesn’t use this would be viewed with a grain of salt.

I agree though that a number of developments would have to happen to make this a reality. I would think that a partnership between NYT and Apple or Nikon could kickstart it though.

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