3 ms·

The goal of C2PA is that cameras will start to emit C2PA credentials. You will then have 3 situations: * C2PA confirms a photo is authentic * C2PA confirms a

The goal of C2PA is that cameras will start to emit C2PA credentials. You will then have 3 situations: * C2PA confirms a photo is authentic * C2PA confirms a photo is AI generated * C2PA missing, you don't know. I reckon we will only see "C2PA missing" being treated as suspect in select situations (perhaps Reuters will require C2PA from their photojournalists, for example)

Retr0id 24d ago
Camera C2PA can never meaningfully confirm that a photo is authentic, it bears about as much credence as EXIF metadata. It's like saying the existence of DRM confirms that a movie hasn't been pirated.
- panarky 24d ago
  C2PA cryptographically guarantees that the bytes came from a hardware/software signer and that the signed payload has not been modified since that signature was applied. So no, C2PA is not as easy to spoof as EXIF. And no, the existence of DRM doesn't validate the integrity or the provenance of the bytes.
  - Retr0id 24d ago
    And what happens when someone tells the hardware signer to sign the bytes of a fake image? What happens when someone extracts the signing key? The presence of cryptography doesn't magically make something trustworthy.
    - panarky 24d ago
      Just because you can imagine how a thing could theoretically be broken does not make it broken. It's like saying a prisoner has the same freedoms as everyone else because he could theoretically escape.
      - lanyard-textile 24d ago
        It's not an apt analogy. The prisoner's every move is guarded; the camera is free in your hands to be disassembled.
      - seplox 24d ago
        We've been here before: https://blog.elcomsoft.com/2011/04/nikon-image-authentication-system-compromised/ https://blog.elcomsoft.com/2011/04/nikon-image-authenticatio...
      - Retr0id 24d ago
        It's not a theory, I've done it. Here's a cryptographically signed + timestamped photo of me winning the lottery: https://verify.contentauthenticity.org/?source=https%3A%2F%2Fretr0.id%2Fstuff%2Fnocors%2FPXL_20260828_135842548.jpg https://verify.contentauthenticity.org/?source=https%3A%2F%2... Would you like to buy my winning ticket from me? (Compare against winning numbers and draw timestamp at https://www.euro-millions.com/results/28-08-2026 https://www.euro-millions.com/results/28-08-2026 )
        deleted 24d ago
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        deleted 24d ago
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        panarky 23d ago
        Prisoners escaping from prison is not a theory either, prisoners have actually escaped. Does that mean all prisoners are free?
        port443 23d ago
        This is a terrible analogy. In cryptography, once any SINGLE person in the world has compromised a signing key, EVERY person in the world can use it. Thus for a prisoner analogy, its equivalent to say once any SINGLE prisoner escapes, EVERY prisoner has the ability to escape. So yes, in this terrible analogy it means all prisoners are free.
    - deleted 24d ago
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    - mrheosuper 23d ago
      I assume the signing key is different from each camera unit(not only model), so if a picture of you winning lottery in US capture by a camera sold to someone in Thailand, it would be extreme unlikely to be real.
      - Retr0id 23d ago
        Why would I use a camera from Thailand for my forgery?
    - artyomsv 23d ago
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    - JacobKfromIRC 23d ago
      This is not the case with current systems, but could future systems be designed to be tamper-evident in a way that makes it impractical to sign fake images or extract the signing key without leaving evidence on the device? If that were the case, I can imagine a subscription service in which you get a camera for some specified period of time, and then return it to the company that sold it for them to verify the camera hasn't been tampered with. Then the company could publish a list of which keys (unique per camera) have been verified to not be tampered with. Maybe this wouldn't stop everyone, but now the person trying to fake images has to re-do the process every so often and I imagine it's more expensive to avoid leaving evidence. This might be too impractical to work, and it would be bad for privacy, but maybe for some people the tradeoffs actually would be worth it, someday. For now, I assume there are much cheaper and easier ways to detect faked images, at least for expert humans.
tyffanypastecf 24d ago
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Retr0id 24d ago

Camera C2PA can never meaningfully confirm that a photo is authentic, it bears about as much credence as EXIF metadata. It's like saying the existence of DRM confirms that a movie hasn't been pirated.

panarky 24d ago
C2PA cryptographically guarantees that the bytes came from a hardware/software signer and that the signed payload has not been modified since that signature was applied. So no, C2PA is not as easy to spoof as EXIF. And no, the existence of DRM doesn't validate the integrity or the provenance of the bytes.
- Retr0id 24d ago
  And what happens when someone tells the hardware signer to sign the bytes of a fake image? What happens when someone extracts the signing key? The presence of cryptography doesn't magically make something trustworthy.
  - panarky 24d ago
    Just because you can imagine how a thing could theoretically be broken does not make it broken. It's like saying a prisoner has the same freedoms as everyone else because he could theoretically escape.
    - lanyard-textile 24d ago
      It's not an apt analogy. The prisoner's every move is guarded; the camera is free in your hands to be disassembled.
    - seplox 24d ago
      We've been here before: https://blog.elcomsoft.com/2011/04/nikon-image-authentication-system-compromised/ https://blog.elcomsoft.com/2011/04/nikon-image-authenticatio...
    - Retr0id 24d ago
      It's not a theory, I've done it. Here's a cryptographically signed + timestamped photo of me winning the lottery: https://verify.contentauthenticity.org/?source=https%3A%2F%2Fretr0.id%2Fstuff%2Fnocors%2FPXL_20260828_135842548.jpg https://verify.contentauthenticity.org/?source=https%3A%2F%2... Would you like to buy my winning ticket from me? (Compare against winning numbers and draw timestamp at https://www.euro-millions.com/results/28-08-2026 https://www.euro-millions.com/results/28-08-2026 )
      - deleted 24d ago
        [deleted]
      - deleted 24d ago
        [deleted]
      - panarky 23d ago
        Prisoners escaping from prison is not a theory either, prisoners have actually escaped. Does that mean all prisoners are free?
        port443 23d ago
        This is a terrible analogy. In cryptography, once any SINGLE person in the world has compromised a signing key, EVERY person in the world can use it. Thus for a prisoner analogy, its equivalent to say once any SINGLE prisoner escapes, EVERY prisoner has the ability to escape. So yes, in this terrible analogy it means all prisoners are free.
  - deleted 24d ago
    [deleted]
  - mrheosuper 23d ago
    I assume the signing key is different from each camera unit(not only model), so if a picture of you winning lottery in US capture by a camera sold to someone in Thailand, it would be extreme unlikely to be real.
    - Retr0id 23d ago
      Why would I use a camera from Thailand for my forgery?
  - artyomsv 23d ago
    [dead]
  - JacobKfromIRC 23d ago
    This is not the case with current systems, but could future systems be designed to be tamper-evident in a way that makes it impractical to sign fake images or extract the signing key without leaving evidence on the device? If that were the case, I can imagine a subscription service in which you get a camera for some specified period of time, and then return it to the company that sold it for them to verify the camera hasn't been tampered with. Then the company could publish a list of which keys (unique per camera) have been verified to not be tampered with. Maybe this wouldn't stop everyone, but now the person trying to fake images has to re-do the process every so often and I imagine it's more expensive to avoid leaving evidence. This might be too impractical to work, and it would be bad for privacy, but maybe for some people the tradeoffs actually would be worth it, someday. For now, I assume there are much cheaper and easier ways to detect faked images, at least for expert humans.

tyffanypastecf 24d ago

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