I'm unwilling to trust a company to provide me with a binary that touches unencrypted data/keys AND also host all my data. It's just too easy to slip in a spec

I'm unwilling to trust a company to provide me with a binary that touches unencrypted data/keys AND also host all my data. It's just too easy to slip in a special backdoor on update (and failing to update = big security risk, too, and generally unworkable for general purpose products for features/OS reasons.) What I want is a trustworthy client, ideally written to an open published standard, which can either backend with a service (with ideally several providers), or with a self-hosted binary (or appliance).