Brian from Backblaze here. > A solution would be then to story copy of the key encrypted on their servers This is what we do. If you set a private passphrase

Brian from Backblaze here. > A solution would be then to story copy of the key encrypted on their servers This is what we do. If you set a private passphrase, then we are keeping your private encryption key for you encrypted with the passphrase on our servers. If you never prepare a restore (or up until you prepare your first restore), your files are unable to be read by malicious hackers that have compromised our systems (if that ever occurs), because you have literally never given us the passphrase. Or put differently, we could not possibly comply with a subpoena for your data because we cannot decrypt it, period. > send you the key when you initiate recovery This is the only part we do not do. Instead, when you provide the passphrase, we only store that passphrase in RAM on our server side for the minimum amount of time possible to decrypt the file or files you have requested, then we purge the passphrase from RAM. After you download the restored file we purge both the passphrase and the decrypted file from our systems and everything returns to the safest state again. Yes, this creates a short window of decreased security (can be as little as 60 seconds). But as long as we weren't compromised during that 60 seconds your data is and will stay totally encrypted. 99.999% of the time Backblaze has no ability to read your data. It is actually 100.0% of the time if you are using Backblaze as a Hail Mary offsite backup in case your house burns down and burns your local backup up. As long as your house never burns down, Backblaze will remain stoically there and encrypted and hackers or the government will have zero ability to ever read your data, period.