Earlier quoted context omitted.
> I never really understood this. Ed25519 keys use SHA-512 and are considered secure. They're still just long secrets, aren't they? No. I find it easiest to keep this straight in my head with a line from the U2 song "The Fly", "a secret is something you tell one other person". You're thinking of Ed25519 private keys, you mustn't tell those to anybody and they're minted as a pair with a public key you can tell to ever…
Overall I agree, but couldn't Edward steal the users' Facebook cookies regardless of WebAuthn? I think those last until the user clicks logout, so many of them will last forever. Additionally, Edward can steal the cookies of every user using Facebook for that hour. But he can only steal the passwords of a small fraction of those users, because only a small fraction will start a new session; most users will use existi…
So, after Edward is discovered, all sessions are remotely logged off and all accounts created during that hour are blocked, asked to confirm their email, phone or even identity, or deleted.
So, after one hour, Edward is left with nothing more than braggable rights. And personal data of billions, but not their passwords.