Great, thanks for answering. Do you have a spec or research paper I can read? I'm quite interested in the topic. Do you think “asymmetry” could be achieved so the secret each user shares doesn’t need to be symmetric?

The research paper is in the OP ("Meteor"). I don't think a spec really makes sense, bit, someone could try. As I tried to explain it's not really practical yet. You can see the code in the repo I posted for an example.