[epistasis]

Have you considered dual browser extensions as in this paper:

https://arxiv.org/abs/1706.05085

>The prototype Horcrux client, implemented as a Firefox add-on, is split into two components, with code that has access to the user's master's password and any key material isolated into a small auditable component, separate from the complexity of managing the user interface.

[varjolintu]

Interesting idea. Gotta read the paper. Thank you.