Spideroak.com has this to say about zero knowledge encryption:
“Zero Knowledge means we know nothing about the encrypted data you store on our servers. This unique design means nothing leaves your computer until after it is encrypted and is never decrypted until it is unlocked with your password on your computer. It’s not just “end to end encryption;” it’s a Zero Knowledge System.”
Spideroak.com, by the way, is a cloud drive service provider. Though, there are some critiques of the way they password protect your local key on your own PC, it is far more secure than Google Drive, Microsoft One Drive, Amazon cloud storage, DropBox, Box.Net, etc…
In short, if you have full control over your encryption keys and the remote service provider does NOT and cannot decrypt your data, then THAT is zero knowledge encryption. Never settle for anything less.