Posted by ComputerGuru 9 hours ago
I already replaced the 'solitaire' games suite with pysol running on WSL2 and it's a vast improvement!
tldr -if MS is going to screw us, why don't we mitigate it by using replacements?
Some proof: https://verify.contentauthenticity.org/?source=https://retr0...
I could also paste a privkey + cert chain in here but el goog's lawyers might not like that.
Being signed with something just means that whoever has that key could've done that. That might be the owner of a specific camera, but it might also be the camera manufacturer, anyone else in the supply chain, or anyone who dumped the key.
Imagine fake evidence signed with the same key as your camera uses being used in court against you. And the court believes it because it has this signature attached and those computers are very secure and all.
Exactly that will happen. Not widespread, of course, but it will.
But what you're talking about is the generative aspect of these photos likely expanding over time. We're seeing that today with the ultra zoom features on some cameras regenerating objects (and especially text). Without the user doing anything the phone will generatively fill in detail, most worryingly text and people. Then there's the Samsung moon issue - taking a photo of a pixelated printout of the moon caused Samsung phones to generate a new image of the moon.
Nobody knows how to make a camera that can distinguish honest vs deceptive photons.
I suppose a dedicated fraudster could still stage an appropriate scene. An appropriately lit matte image might even suffice.
If we as a society deemed it necessary, the camera manufacturer could also provide a list of keys for devices they have manufactured. And an image/key could be provided, and the manufacturer could verify the authenticity that way.
The TPM signing could be tied into the sensor hardware itself, making it difficult, but not impossible, to sign arbitrary images with the TPM.
If the TPM signs the original image taken by the camera, then even the slightest image processing on another device would invalidate the signature. Routine changes like cropping, scaling, converting between image formats / quality levels, or applying image filters would invalidate the signature.
An adversary can manipulate the date/time settings on the camera and forge evidence to frame someone. "This cryptographically signed photo, with timestamp, proves that you were here at this time!"
And camera sensors can get damaged and need replacement. But if replacement of the TPM-and-sensor chip is allowed, then you can just as well replace it with a sensor from another camera. In which case a signature from a specific TPM+sensor doesn't prove that a specific camera took the photo, at best it might be evidence that a specific camera model took the photo.
If the manufacturer will happily ship a replacement TPM+sensor for a specific camera, someone can fraudulently claim that their sensor is broken and be given a new TPM+sensor for the same camera. And there will now be multiple TPM+sensors in existence that have the same key. Since this module can be switched between cameras, there could be multiple cameras that signed a given picture.
To ship (identical) replacement TPMs, the manufacturer would also need to know the private keys of all the cameras, so the manufacturer could forge arbitrary signatures at will.
Finally maybe the manufacturer doesn't want to deal with the above problems and decides that repairing the camera's TPM is not allowed after all, or that only the manufacturer is allowed to repair a camera, but then they may be in violation of right-to-repair laws in several jurisdictions.
If I need to reset TPM, how do I reclaim photos I took previously?
If a key was reset, a revocation of the original key could be issued, showing that the key was associated with the device for this particular time span. And then the new key registered.
This is ripe for abuse though, so resetting a TPM might not be accepted for this use case. I'm not certain in which case you'd want to reset a TPM for this use case though. Unless you took enough photos with the device to risk a birthday attack if you were using something like ECDSA.
People take RAW photos. Load it up in a RAW editing tool. Manipulate it. Then load it in Gimp. Manipulate some more.
Will the final result have the signature?
And if it does, what use would it be?
Each piece of software in the chain must use TPM-like technologies (yes, even GIMP) to make sure it's running a "legitimate" build of the software, on "legitimate" hardware, and re-sign the file at each step along the way (using keys provisioned during some flavour of remote attestation flow, or using a RA-authenticated remote-signing oracle).
The final file embeds every preceding manifest, so you can "verify" all the way back to the original.
If this all sounds patently unworkable, that's because it is.
No. You'd only ever be able to show that key material belonging to $specific_camera was used to sign/mark the image.
Was the camera manufacturer breached? Did somebody on the factory floor steal some keys during the provisioning step? Or did somebody build their own photo-sensor simulator and plug _that_ in to the camera's motherboard to feed it a "real" image? Before going _that_ far, just point the unmodified camera at a sufficiently high resolution display...
"I think it would be nice if all typewriters had their unique fine-detail type artifacts registered with the government. You could tell exactly who authored a given document."
I think it would be nice if you took these ideas back to Stalinist Russia where they belong.
Shipping the watermark generator on user's machine would make it very easy for someone motivated to find how it works and write a "watermark remover".
