[kakwa_]

Backblaze actually permits that:

You have the option with Backblaze to add an additional layer of privacy via a user-selected passphrase. This passphrase will be used to encrypt your private key. This passphrase is your responsibility to remember and safeguard. This is important: if you forget or lose this passphrase there is no way that anyone, including Backblaze, can decrypt, and thus restore, your data. When you choose to add your own passphrase there is no “forgot passphrase” mechanism as Backblaze does not know your passphrase.

https://www.backblaze.com/backup-encryption.html