7 ms·

Signing things by default has repeatedly been found to have serious unintended consequences. Do you really want your leaked/stolen photos to be undeniably linke

Signing things by default has repeatedly been found to have serious unintended consequences. Do you really want your leaked/stolen photos to be undeniably linked to you? https://blog.cryptographyengineering.com/2020/11/16/ok-google-please-publish-your-dkim-secret-keys/ https://blog.cryptographyengineering.com/2020/11/16/ok-googl...

postit 7d ago
It reminds me of the era when the Stasi kept archives of typewriter samples and typefaces so they could trace the authors of anonymous letters deemed subversive.
- netsharc 7d ago
  Samples, or sampling of each typewriter's idiosyncracies? This post https://foxfire.blog/explorations/the-typewriter-that-became-a-weapon https://foxfire.blog/explorations/the-typewriter-that-became... claims "specific machine": > The forensic science behind this was genuinely elegant. No two typewriters print identically. The mechanical tolerances of individual typebars—those metal arms that swing up to strike the ribbon—create unique signatures. Forensic document examiners look at three primary characteristics: alignment (whether a letter strikes slightly above or below the baseline), impression (whether one side of a letter prints darker than the other due to uneven wear), and damage (a chipped serif, a broken bowl on a lowercase “g”, a filled-in counter on an “e”). Taken together, these micro-imperfections form a pattern as distinctive as a human fingerprint—or so the authorities claimed. > The East German Stasi took this principle to its industrial extreme. They maintained an exhaustive registry of type samples, a vast database of typewriter fingerprints. When a dissident pamphlet surfaced, the Stasi could compare its letterforms against their archive and, in theory, trace the text back to the specific machine that produced it. The countermeasure was ingenious in its simplicity: dissidents sought out pre-communist typewriter models—early Mignon or Ideal D machines manufactured before the registry existed. A typewriter without a file was a typewriter without a name. It could speak and not be traced. Since they had control of commerce, I suppose it was possible to intercept every typewriter and "fingerprint" it before it is sold, or even tweak the typewriter to produce something unique (e.g. chipping a typebar so it prints a particular letter distinctly). Hah, needing to register your name/address to buy a typewriter feels spooky too. And if it gets stolen, you'd have to tell the authorities that it's no longer in your possession.
mike_hearn 7d ago
Maybe cryptographers think this way, but I'm struggling to think of a case where a normal person had genuine photos leaked and then just baldly denied everything. Deniability isn't an option most people use or want to use in practice. On the other hand, images faked by AI is a real problem.
- smalltorch 7d ago
  I don't think it's really the utility of deniability, rather a slippery slope of and loss of freedom from a mechanism that stamps every photo taken and silently cryptographically ties it to the photo taker. That could obviously be used for good or bad purposes. Reminds me of tracking dots in printers. It was implemented to provide a way to track a document to its source.
- zbentley 7d ago
  > a case where a normal person had genuine photos leaked and then just baldly denied everything "Genuine" is doing a lot of work in that sentence. A big part of the threat model for image provenance/signing/similarity diffing is identifying when images aren't genuine--if they're from elsewhere than they're claimed to be from, or have been modified. You're right that there are privacy/security costs to attributability, and that it's not always the right thing to do. I hope that keeping provenance information either entirely cryptographic in nature (okay, the image has a signature--you can't determine anything about that signature other than "signed with this key y/n" when you present a key) or reducing identifying or fingerprintable information presence in provenance metadata is sufficient to mitigate some of those concerns. Dr. Neal Krawetz has written and researched a lot about this topic: https://hackerfactor.com/blog/index.php?/archives/1069-The-Big-Bulleted-List.html https://hackerfactor.com/blog/index.php?/archives/1069-The-B... https://hackerfactor.com/blog/index.php?/archives/1098-Metas-Un-Stable-Signature.html https://hackerfactor.com/blog/index.php?/archives/1098-Metas... https://www.hackerfactor.com/blog/?/archives/529-Kind-of-Like-That.html https://www.hackerfactor.com/blog/?/archives/529-Kind-of-Lik...

postit 7d ago

It reminds me of the era when the Stasi kept archives of typewriter samples and typefaces so they could trace the authors of anonymous letters deemed subversive.

netsharc 7d ago
Samples, or sampling of each typewriter's idiosyncracies? This post https://foxfire.blog/explorations/the-typewriter-that-became-a-weapon https://foxfire.blog/explorations/the-typewriter-that-became... claims "specific machine": > The forensic science behind this was genuinely elegant. No two typewriters print identically. The mechanical tolerances of individual typebars—those metal arms that swing up to strike the ribbon—create unique signatures. Forensic document examiners look at three primary characteristics: alignment (whether a letter strikes slightly above or below the baseline), impression (whether one side of a letter prints darker than the other due to uneven wear), and damage (a chipped serif, a broken bowl on a lowercase “g”, a filled-in counter on an “e”). Taken together, these micro-imperfections form a pattern as distinctive as a human fingerprint—or so the authorities claimed. > The East German Stasi took this principle to its industrial extreme. They maintained an exhaustive registry of type samples, a vast database of typewriter fingerprints. When a dissident pamphlet surfaced, the Stasi could compare its letterforms against their archive and, in theory, trace the text back to the specific machine that produced it. The countermeasure was ingenious in its simplicity: dissidents sought out pre-communist typewriter models—early Mignon or Ideal D machines manufactured before the registry existed. A typewriter without a file was a typewriter without a name. It could speak and not be traced. Since they had control of commerce, I suppose it was possible to intercept every typewriter and "fingerprint" it before it is sold, or even tweak the typewriter to produce something unique (e.g. chipping a typebar so it prints a particular letter distinctly). Hah, needing to register your name/address to buy a typewriter feels spooky too. And if it gets stolen, you'd have to tell the authorities that it's no longer in your possession.

mike_hearn 7d ago

Maybe cryptographers think this way, but I'm struggling to think of a case where a normal person had genuine photos leaked and then just baldly denied everything. Deniability isn't an option most people use or want to use in practice. On the other hand, images faked by AI is a real problem.

smalltorch 7d ago
I don't think it's really the utility of deniability, rather a slippery slope of and loss of freedom from a mechanism that stamps every photo taken and silently cryptographically ties it to the photo taker. That could obviously be used for good or bad purposes. Reminds me of tracking dots in printers. It was implemented to provide a way to track a document to its source.
zbentley 7d ago
> a case where a normal person had genuine photos leaked and then just baldly denied everything "Genuine" is doing a lot of work in that sentence. A big part of the threat model for image provenance/signing/similarity diffing is identifying when images aren't genuine--if they're from elsewhere than they're claimed to be from, or have been modified. You're right that there are privacy/security costs to attributability, and that it's not always the right thing to do. I hope that keeping provenance information either entirely cryptographic in nature (okay, the image has a signature--you can't determine anything about that signature other than "signed with this key y/n" when you present a key) or reducing identifying or fingerprintable information presence in provenance metadata is sufficient to mitigate some of those concerns. Dr. Neal Krawetz has written and researched a lot about this topic: https://hackerfactor.com/blog/index.php?/archives/1069-The-Big-Bulleted-List.html https://hackerfactor.com/blog/index.php?/archives/1069-The-B... https://hackerfactor.com/blog/index.php?/archives/1098-Metas-Un-Stable-Signature.html https://hackerfactor.com/blog/index.php?/archives/1098-Metas... https://www.hackerfactor.com/blog/?/archives/529-Kind-of-Like-That.html https://www.hackerfactor.com/blog/?/archives/529-Kind-of-Lik...