This gets complex fast. The access control list needs to travel with the data. Revocation can theoretically take forever (until all offline clients get back onl

This gets complex fast. The access control list needs to travel with the data. Revocation can theoretically take forever (until all offline clients get back online). Onwer signing content is great but breaks rule 4 (It should support collaboration). I've been working on my own personal-use app for my twin and I to collaborate on documents from different continents so pretty close to the problem.