Congrats, this looks really great! Do you plan turning this into a product/service or is it a side project? I think there's a real market for secure alternatives to popular cloud services so I hope this will be successful. Personally, I moved most of my data and services (G-Mail, Dropbox, AWS) away from the US to European alternatives, which fortunately stepped up their game in the last years (IMHO) and are often quite usable. I haven't found a good alternative to G-Docs for collaborative editing though, so pretty excited about something like this. I think a traditional encrypted backend data store would be more adequate for most users though.