Wow, that's a neat idea and a very good execution. If only it didn't had to "...Some Javascript that calls into the browser’s Web Cryptography APIs" and had all

Wow, that's a neat idea and a very good execution. If only it didn't had to "...Some Javascript that calls into the browser’s Web Cryptography APIs" and had all the code inside the HTML that would be great. Completely self-sufficient and offline, without dependency to the browser(s).