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Comment by mmalone | Hacker News Reader

I think TOFU would be really problematic for browsers & the Web PKI trust model. At this point Web PKI is dealing with attacks from nation-states and other advanced threats that end-users aren't really in a position to handle themselves.

Like, just last week the browsers had to remove a certificate authority from their root cert programs because Kazakhstan was issuing certificates to MiTM traffic. A TOFU model would make it a lot harder to detect and remediate this sort of attack and lots of other relevant attack vectors.

We'd also need to re-solve a bunch of adjacent problems like revocation, renewal/rotation, and transparency, which would probably mean re-introducing the sorts of centralized architectural components and processes that I'm assuming you're trying to eliminate with TOFU.

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All those points can be summed up as: The point of web PKI is that the decision of who to trust and who not is not supposed to rest at the end user but at some central authority.

Then however, we get to the political question who exactly that central authority should be and why.

> Like, just last week the browsers had to remove a certificate authority from their root cert programs because Kazakhstan was issuing certificates to MiTM traffic.

I may have misunderstood the incident, but wasn't it such that the CA was not even one of the built-ins, but a "custom" root CA that all users were required to install on their systems? As such, the block was more equivalent to block a specific to TOFU key.

Of course, blocking the MITM CA won't magically turn off the ISP's MITM proxy. It will simply make it so that kazhakh citizens can't access any web sites at all until the government hopefully caves and turns off the proxy.

Yea you’re correct. They were forcing people to add a CA. So this was not a great example.

I wouldn’t say the centralization of Web PKI is by design so much as it is (was?) by necessity. There’s a crypto conjecture called Zooko’s Triangle that says there are three desirable properties for a naming system: human-meaningful, secure, and decentralized. Zooko’s conjecture is that you can only have two. Web PKI picks secure & human-meaningful. Simple PKI (like TOFU) picks secure & decentralized (the names aren’t actually human-meaningful since you’re really trusting a public key which is a big random number, not a domain name). DNS picks human-meaningful and decentralized.

More recently, Aaron Schwartz realized you can “square the triangle” using blockchain. So it appears to be technically possible to have all three now, but there are other hurdles. In any case, simple public keys aren’t a silver bullet. Just a different set of compromises.

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