Trusted URLs via Cryptographic Signatures
blog.certisfy.com
blog.certisfy.com
Web of trust use case example: https://bsky.app/profile/bitlooter.bsky.social
Experimenting with Keybase key holders as CAs:
https://www.reddit.com/r/Keybase/comments/1q5ys71/using_keyb...
Cryptographic Implementation of Exclusivity Agreements: https://github.com/CipherTrustee/certisfy-claim-recipes/tree...
Build Your Own Trust Chain: https://blog.certisfy.com/2026/04/build-your-own-trust-chain...
Some other examples of how you could leverage it: https://blog.certisfy.com/
Happy to answer questions.
But I wouldn't characterize it in terms of being hard.
It's been a work in progress for many years,... so more of a problem solving and exploratory endeavor.
it's basically an OIDC provider as an identity wallet using verifiable credentials, but I've got a "share link" system built in where you can share specific credentials/proofs with others.
If I've understood it, certisfy makes it possible to do something like this:
I-was-there-and-saw-this-happen(https://site.com/some-page-with-an-image)
I'm building something similar. I've been avoiding URLs though because the above arrangement depends on site.com reliably serving the same image to all users. If you end up with a different image when you browse there, and you can falsify the claim, you don't know if I'm a liar, or if the underlying site changed.
So my plan is to gossip fuzzy hashes around and use patterns in the data (rabin fingerpints, perceptual hashes, etc) to then go look up whether there are any claims about that data, attaching them after the DOM has rendered. Or maybe there's no DOM, maybe you're looking at a physical page of a book or something.
Do you have any thoughts about what it would take to support claims about a site's content in addition to claims about its URL? I'm imagining something like:
contains-an-image-with-hash(https://site.com/some-page-with-an-image, 0xabc123456def)
I-was-there-and-saw-this-happen(0xabc123456def)
1. What is the attester (signer) attesting to, exactly?
This URL example is exactly this problem. And if you're really precise about it, they get less and less useful: "I attest that when I accessed this site at XYZ timestamp, it contained ABC content, and I saw ABC happen in person." or maybe alternatively to get away from the URL control, "I attest that these three non-malicious archives of this URL at this timestamp..."
And 2. Why should I trust the attester?
As for getting less useful with more precision, I'm not sure I agree. If they're precise enough, you can do predicate logic on them (e.g. prolog):
- mycologist attests about an image: this mushroom is edible
- image ends up on a social feed, a passerby realizes that it's the same image (modulo compression) and attests to that sameness
- I run across the image on a social feed. I have weak trust with the passerby but strong trust with the mycologist. My client can computationally verify the sameness claim, so I don't need strong trust for the passerby (I just needed them for a hint of what my client should verify).
I can then conclude that the pictured mushroom is edible, even though it's not actually bitwise identical to the one that the mycologist asserted about. Without precision, you can't get the predicates to line up for such a derivation.
Unfortunately, AMP itself was controversial and the system was not really adopted elsewhere, but it is something.