Office 365 Hold Your Own Key
Encryption is hard. There is really no way around that fact.
One of the great benefits of Office 365, or any cloud product, is that these complex solutions are deployed and maintained for you by those who are best qualified to make them work. The downside to having someone else deploy and run your IT solutions is the lack of control you have over your information. You don’t really know who has access to your information when you’re moving it to the cloud.