Proton Mail discloses user data leading to arrest in Spain

I use Proton to protect myself from Google, Microsoft, advertisements, tracking, terrible, slow, “too much padding everywhere” UI, my emails/data being sold to 3rd parties, etc. I’m not worried about Proton cooperating with law enforcement agencies to catch criminals.

However.

What if say, russia/nk/china wants to catch somebody some journalist for speaking truth about their regimes? Or, like say, Jason Bourne exposing some IronHand in “democratic” country like USA? How can we protect good actors without enabling adversaries to do “bad stuff”? Is it even possible? I still don’t know the answer…

They could but then you open the mobile app or another computer and the key just isn't there. They could generate one subkey for each device but then you risk user emails being impossible to decrypt if they ever lose that device. Hell I'm a programmer and I somehow managed to get my own master key deleted because I ran smack into some gpg bug which I then reported and sent a patch for. If I can't do this without deleting my keys and being forced to revoke them from keyservers immediately after publishing, what hope do end users have?

The most secure solution is to generate keys on an OpenPGP smartcard like an NFC enabled YubiKey and use that key everywhere. Even that's incompatible with maximum reliability: YubiKeys can and will eventually fail and when they do your keys are gone. So you can't generate the encryption subkey on the smartcard, you need to generate it on a secure device, back it up to paper just like the master key, and then copy it to the smartcard. Otherwise you risk being unable to decrypt data later.

It's an incredibly hard problem and it's full of tradeoffs. I can at least respect their attempt to solve the problem.

> you mean non-governmental

I would say most people are concerned with dragnets, not targeted attacks. There's quite a lot you can hide from the government in terms of dragnets, in the same way you'd hide from big tech.

"Hide" isn't the right word. "Defend from" I think is probably better. Defending our constitutional rights from government and defending our privacy from big tech.

I'm actually perfectly okay with governments in targeted attacks (where a warrant is reasonably given). I'm just not okay with police being lazy.

> Is this password-derived key the "account key" which I see in the Proton Mail settings interface?

No, the account key is an OpenPGP key which is encrypted with a key derived from your password. The "key encryption key" is not separately visible. The address keys are in turn encrypted using the account key. (The account keys are also used to encrypt your contacts, for example, which are shared between all your addresses - while the address keys are specific to an email address and are used to encrypt emails etc.)

> Please clarify what key derivation function is being used.

We use bcrypt, in addition to the OpenPGP S2K (i.e. the bcrypt output is fed as the "password" to OpenPGP's key encryption).

We are in the process of rolling out updates to OpenPGP.js and GopenPGP which support Argon2 for the OpenPGP S2K step, after which we'll start using that - but we aren't quite yet.

> Are there instructions for verifying that all this is happening? I think a lot of folks on HN won't be convinced otherwise.

Take a look at https://github.com/ProtonMail/WebClients/blob/main/packages/..., for example. Though to be honest, if you want to verify that we aren't sending the password to the server anywhere, in principle you'd have to check the code of the entire web app (or whichever app you're using). It's all open source, but it's a lot of work, of course. But you can also check the latest audit report: https://proton.me/blog/security-audit. They also verified all of this stuff.

> It's just that I'm going to create an OpenPGP identity for things like signing code commits on git, signing packages I publish. (...) So I was really hoping to be able to use Proton Mail with this identity instead of the key pair that's generated for the account.

Yeah, I understand. Though the typical advice from a cryptographer's perspective would be, it's better to use separate keys for separate purposes; and the simplest way to do that is to generate separate OpenPGP certificates, so that's what we'd generally recommend. But, if you want to generate separate subkeys and sign them all using a common primary key, that's also reasonable enough. And, we can improve the documentation on that, although it's a bit of a niche use case (not for HN of course, but for the general audience it is).

> Thanks for reaching out here on HN. I've been a really happy Proton Mail customer and now I'm even happier.

Thanks, glad to hear! :)

Thanks for clarifying.

> although it's a bit of a niche use case (not for HN of course, but for the general audience it is)

No doubt about that. Safe to assume that 99% of your users will not know or care about this. That's why I want to thank you for supporting this advanced key management feature for those of us who want it. To me that's evidence that Proton Mail takes OpenPGP seriously.