Not only for chat apps and email services, literally all user data on servers should be encrypted with the decryption key only on the user's devices. It should

Not only for chat apps and email services, literally all user data on servers should be encrypted with the decryption key only on the user's devices. It should basically be impossible to identify a user based on the data that a service provider has. The idea is similar to that of ZeroDB, but it extends beyond databases to everything related to a user such as files related to a user.