I’m trying to create a web app that involves sharing of user-generated content, but one of the goals is that the service host operator should be blind to the content. Only authorized users should be able to see the content shared with them. This implies the content must be encrypted at rest, and users must hold custody of their private signing key.

I figure the situation requires an open source browser extension to hold onto a user’s keys and decrypt content for them. The web app would still be able to browse all of the site’s metadata, but any plaintext content must be siloed in the extension. The reason for using an extension is that the source code would be open source and independently verifiable, while building the same functionality into the web app would require trusting the host to serve the code you expect.

Do you think that’s a reasonable tradeoff or is this asking too much from users?

The other option would be just requiring users to download an open source app for content viewing.

EDIT: Perhaps an important followup: are you OK placing trust in the host to never access your confidential data if it means you don’t have to install additional client software or worry about verifying that client software’s authenticity?

  • theherk
    3·
    2 hours ago

    It doesn’t. The code your site provides is downloaded by your client’s browser. It uses a key on their side that is never sent back to your server. Same as if you did it with an extension or application. This is well trodden ground, and used across the internet such that hosts have zero knowledge of their users’ data aside from in its encrypted state.

    Actually, let me give a little ground here. There is a subtle but real benefit to an extension or signed application. With just JavaScript, a server could on a new page load deliver an altered code that would introduce a compromise. If that is the threat you want to mitigate for, you’re onto something. If you’re talking high stakes, and you make it clear this is the threat for which you’re protecting users, then I could be convinced.

    • tatterdemalion@programming.devOP
      31·
      2 hours ago

      The point is you can’t prove the server won’t serve you code that won’t take your key and send it somewhere arbitrary.

      • theherk
        2·
        2 hours ago

        Oh yeah. I had just edited to identify that. And if this is the threat for which you’re protecting, this does make sense.