[arielweisberg]

This can be implemented without storing it. They could store a hash. No idea what they actually do.

[charcircuit]

A hash of a public identifier like an email is personally identifiable data.

[jounker]

Isn’t the entire point of a cryptographically secure hash that you can’t derive the original information?

[charcircuit]

You can't derive the original better than guessing. With public identifiers you can just take a list of them and guess with those. If someone asks for your email they can hash it themselves and compare it against whatever databases.

[pfortuny]

You can always encrypt with a public key instead of hashing.

[pbhjpbhj]

You mean 'as well as', right?

[pfortuny]

No, I mean encrypting (using a random padding like OAEP-RSA) gives an undecipherable item.