My aim is to do something similar to how Proton encrypted emails: keep it simple and user-friendly, so that basically everyone can switch to it from Google/Typeform.

Of course, there's some compromises. You can't really do integrations, since the server doesn't have the raw responses to send anywhere. But there's still tons of use cases where Palform's features suffice.

The encryption is powered by the amazing Sequoia PGP library and simply uses OpenPGP. I know it's not a perfect protocol, but it's been around for ages and audited several times. Users need to be able to trust Palform, and a DIY obscure cryptographic system would make that hard. Plus, this way you can import + export your keys and everything stays interoperable. It even has webhooks, so your servers can store PGP keys and you can decrypt the form responses yourself.