The bridge does the decryption using credentials you give it locally. Sorry for mentioning “auth”. I should have mentioned encryption instead.
Regarding the rest, it comes down to the zero access mailbox encryption’s implementation details. In all described scenarios, you’re not really using your master password as the “key” for your mailbox. But in proton’s and similar services’ case like Tuta, this is true. Any “zero access” service provider offering IMAP access without a bridge is simply lying to you as IMAP (the protocol itself) requires server-side decryption of the content, even if SMTP doesn’t. (Btw, SMTP is really an artificial limitation. Just not IMAP. If they give you smtp access, it wouldn’t send encrypted mails unless specifically configured to do so but would otherwise be the same.)
What you described is encryption at rest, but not zero access encryption (which is what Purelymail does btw).
Whether all this is needed and all depends on your threat model. I think most tech-savvy folks would be happy with something like Purelymail or Migadu tbh…
The bridge does the decryption using credentials you give it locally.
Are you reading what I’m typing? I just described the full process they do on their apps and what can be done over IMAP to give you the same level of protection that Proton offers.
Besides, Proton doesn’t even provide zero access. In Proton there’s a bunch of data like e-mail headers that is NOT encrypted at all and they say it:
Any generic IMAP/SMPT provider + Thunderbird with PGP provides the same level of security that Proton provides, assuming they didn’t mess their client-side encryption/decryption/key storage in some way. PGP is making sure all your e-mail content is encrypted and that’s it, doesn’t matter if it’s done by Thunderbird and the e-mails are stored in Gmail OR if it’s done by the Proton bridge and the e-mails are on their servers, the same PGP tech the only difference is the clients.
One key aspect that you seem to be missing is that Proton encrypts every mail, including those sent by or sent to unencrypted providers using your pgp key before storing them on the server. This isn’t a case scenario that can be handled without using a bridge. Thunderbird or any other mail client won’t know how to handle that.
What you described only solves the end-to-end encryption portion of the problem Proton is trying to solve. Not zero access.
Yes, mail headers are unencrypted. They never claim otherwise and neither did I. If it were encrypted, it wouldn’t be interoperable, which is something you want it to be as well right? I’ve always been talking about the mail content itself. Unencrypted mail headers don’t make it “not zero access”.
I feel like you’re just not the target audience for Proton. I just use Proton because I’m fine with the web UI and Proton Unlimited is mostly good value for me. I do also pay for Purelymail as i have a few domains and they’ve been wonderful too.
One key aspect that you seem to be missing is that Proton encrypts every mail, including those sent by or sent to unencrypted providers using your pgp key before storing them on the server. This isn’t a case scenario that can be handled without using a bridge
Yes it can, and I explained how. Maybe you’re the one not understanding how Proton actually encrypts emails sent by unencrypted providers/people…
There’s guide here explaining this in detail and providing an implementation example with Dovecot. This can be also done when a message is received by the MTA (before it is filed / stored by Dovecot) like discribed in this guide for Exim here. The process should be the same for Postfix.
The bridge does the decryption using credentials you give it locally. Sorry for mentioning “auth”. I should have mentioned encryption instead.
Regarding the rest, it comes down to the zero access mailbox encryption’s implementation details. In all described scenarios, you’re not really using your master password as the “key” for your mailbox. But in proton’s and similar services’ case like Tuta, this is true. Any “zero access” service provider offering IMAP access without a bridge is simply lying to you as IMAP (the protocol itself) requires server-side decryption of the content, even if SMTP doesn’t. (Btw, SMTP is really an artificial limitation. Just not IMAP. If they give you smtp access, it wouldn’t send encrypted mails unless specifically configured to do so but would otherwise be the same.)
What you described is encryption at rest, but not zero access encryption (which is what Purelymail does btw).
Whether all this is needed and all depends on your threat model. I think most tech-savvy folks would be happy with something like Purelymail or Migadu tbh…
Are you reading what I’m typing? I just described the full process they do on their apps and what can be done over IMAP to give you the same level of protection that Proton offers.
Besides, Proton doesn’t even provide zero access. In Proton there’s a bunch of data like e-mail headers that is NOT encrypted at all and they say it:
Any generic IMAP/SMPT provider + Thunderbird with PGP provides the same level of security that Proton provides, assuming they didn’t mess their client-side encryption/decryption/key storage in some way. PGP is making sure all your e-mail content is encrypted and that’s it, doesn’t matter if it’s done by Thunderbird and the e-mails are stored in Gmail OR if it’s done by the Proton bridge and the e-mails are on their servers, the same PGP tech the only difference is the clients.
One key aspect that you seem to be missing is that Proton encrypts every mail, including those sent by or sent to unencrypted providers using your pgp key before storing them on the server. This isn’t a case scenario that can be handled without using a bridge. Thunderbird or any other mail client won’t know how to handle that.
What you described only solves the end-to-end encryption portion of the problem Proton is trying to solve. Not zero access.
Yes, mail headers are unencrypted. They never claim otherwise and neither did I. If it were encrypted, it wouldn’t be interoperable, which is something you want it to be as well right? I’ve always been talking about the mail content itself. Unencrypted mail headers don’t make it “not zero access”.
I feel like you’re just not the target audience for Proton. I just use Proton because I’m fine with the web UI and Proton Unlimited is mostly good value for me. I do also pay for Purelymail as i have a few domains and they’ve been wonderful too.
Yes it can, and I explained how. Maybe you’re the one not understanding how Proton actually encrypts emails sent by unencrypted providers/people…
In asymmetric cryptography the public key is used for encryption, then the related private key is used for decryption. This means the server just has to know your public key to be able to safely store incoming email from unencrypted providers. The Thunderbird that has your private key can decrypt the e-mails later on. This is exactly what Proton does but the decryption part is handled by the bridge.
There’s guide here explaining this in detail and providing an implementation example with Dovecot. This can be also done when a message is received by the MTA (before it is filed / stored by Dovecot) like discribed in this guide for Exim here. The process should be the same for Postfix.