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Comment by layer8 | Hacker News Reader

This may actually be a good point. Instead of storing your recovery address, they could only store a hash of it, and require an email to be sent from the recovery address to initiate the recovery process. Still not completely zero-knowledge, but an improvement.

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We do offer alternatives to email addresses and phone numbers when it comes to recovering account access - you can also use a recovery phrase: https://proton.me/support/set-account-recovery-methods#how-t...

Given the typical length and character set of email addresses, 'reversing' the hash can be considered trivial.

Not if done properly, with a hard hash function and a length requirement on the email address.

Presumably you’d choose a long localpart for the recovery address. Proton could even require that.

Not every mail system supports that and the longer & harder to guess it is the more likely it is that whatever disaster lead to needing the recovery process would also lose that information.

The rules on how long a local-part is allowed to be are very clear (https://datatracker.ietf.org/doc/html/rfc5321#section-4.5.3....), and once you’ve registered the address you would know that it works. You’d write it down and/or store it in your password manager like you would with any passphrase. I really don’t see the problem.

It’s not a question of whether it’s technically possible but practical to expect people to maintain a recovery address which is not otherwise used or guessable. If you can pull it off, sure, but from a security perspective I’d probably be looking for a way to avoid email at all for this mechanism since it just wasn’t designed around address privacy.

Or you could get a free proton email as recovery.

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