"The main difference between Confidant and the others is that Confidant is purposely not cloud agnostic, choosing to use AWS’s features to deliver a more integrated experience. By leveraging AWS’s KMS service, Confidant is able to ensure the master encryption key can’t be stolen, that authentication credentials for Confidant don’t need to be distributed to clients, and that authentication credentials for Confidant clients don’t need to generated and trusted through quasi-trustable metadata."

Confidant is purposely tied to AWS so that it can rely on KMS for its master key and for authentication.