alt Hacker NewsThe “4” affair did make me wonder… as a non-expert, I’d always kind of assumed that—with all the ceremony around key ceremonies and all—there might be some way to provably assert the set of techniques used to arrive at the key in the first place. XYZ hardware-signed source of entropy was sampled at DEF time and input into ABC signed chunk of algorithm to arrive at the private key…
In fact I assumed that’s why somebody might explicitly choose “4” as their key: to make it as easily detected as “TK” in a copy edit, or a prefix-designated API key in a repo, or an “@example.com” that slides by into a serious environment.
We really go on a pinky swear across the public CA ecosystem?
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You're looking for https://www.ietf.org/archive/id/draft-ietf-lamps-csr-attesta.... It's gotten enough renewed attention in the wake of the eMudhra fiasco that I'm reasonably optimistic about it becoming required for intermediates.
You could certainly use zero knowledge proofs to prove some statements about the secret key, like requiring it to be roughly a 1:1 ratio of 0s and 1s and the longest run of the same bit is not significantly larger than the typical cake you’d expect in a random string that size. I think if I were trying to enforce a minimum level of security then I might take that route, requiring that the key passes zero-knowledge proofs of various statistical tests of randomness.
By pigeonhole principle, nearly all numbers have to have a Kolmogrov complexity within some constant of their own length, meaning they are algorithmically random and will by definition pass every statistical test of randomness, so you lose surprisingly few bits entropy per assertion this way.