The basic principles of end-to-end encryption aren't particularly difficult if there are only two communicating parties[1]. However, you do need an architecture

The basic principles of end-to-end encryption aren't particularly difficult if there are only two communicating parties[1]. However, you do need an architecture that supports it. I suspect a lot of online communications and data hosting services now have a barrier to implementing E2E simply because they already have established infrastructure and software architecture but everything was originally specified to support a centralised system. You can't just drop in a different library or edit a handy configuration file to turn one type of system into the other. Fundamentally, you need to build something new and with a different architecture to work on an E2E basis, which is a major investment and a significant risk if you already have an otherwise successful product operating on a large scale. The main challenge with E2E, as far as I'm aware, is still how to scale up the basic principle effectively as the number of participants increases. However, none of this affects the iCloud functionality I've been referring to, where essentially you're only storing data for one party anyway. [1] This statement is made in the context that encryption in general is a field where you really want people who know what they're doing implementing everything and if you don't have experts in-house then you should probably use someone else's tried and tested implementation instead of attempting a home-grown version.