I want to do this for some sets of data, but the problem is how to make it easy for the users to manage their encryption key - It can't be saved to the database

I want to do this for some sets of data, but the problem is how to make it easy for the users to manage their encryption key - It can't be saved to the database, or the whole thing is pointless. I've considered: 1. having an input form for them to enter the key when they access sensitive data (but then they have to copy paste that from somewhere else or remember it - not very convenient) 2. A local client program that does the encryption, then saves the data to the web. The more I think about it, I suspect the people who want encryption are not going to be my customers anyway (why would they encrypt and then upload to a cloud service?)