Personally, I think it’s a bit weird that we’re not given the actual private key file – but I guess that’s okay given that they cannot decrypt any files without the password that protects the key file.

Carbonite, for example, gives the user the full openssh key while Backblaze just silently dumps a public-key file in the installation directory.

The private key option that I think you are talking about is an extra layer of security where you actually provide the encryption key that is used to store your data securely (instead of the common one that Backblaze would use).

Take a look at this:

http://blog.backblaze.com/2008/11/12/how-to-make-strong-encryption-easy-to-use/

Now, my assumption is if you get a DVD or USB drive with your data, there are two ways that they can do it:

1. You have to give them your private key before they send you your data. Your data comes on the DVD or USB drive unencrypted.

2. There is some mechanism on the DVD or USB Drive where your data is encrypted and you can provide your private key to get at your data.

I seem to remember that Backblaze does (1) right now but might be working on a mechanism to do (2). Not sure if they have done that yet.

Maybe someone over there can comment.

I haven’t look into it, I’m just guessing