I am interested in backing up my personal computer and my web server with CrashPlan.
As I understand it, CrashPlan supports 3 levels of data security:
- Encrypt files locally, using a key provided by CrashPlan. CrashPlan
has the key in (essentially) plaintext. So they can clearly see your
- Encrypt files locally, using an "archive key" – a key generated
locally from a password. CrashPlan servers only ever see the archive
key in hashed and salted form, so presumably they can't look at your
- Encrypt files locally using a custom key. The user defines the key
and it never leaves the local machine.
It seems like the difference between option 2 and 3 is that, which option 3, there is the onus of me needing to keep a copy of this keyfile, which is cumbersome (vs. a password). My question is this: how much more secure is option 3?
If I have a 448 bit hashed and salted key and I have the encrypted files, how hard is it to attack and key and decrypt the files?
How much easier does this task become if the attacker knows what some of the unencrypted files look like? (For example, if I upload my whole disk to CrashPlan and it includes some standard Windows system files that every attacker would presumably know both the pre and post image of).
The cipher they are using is Blowfish.
Also, does CrashPlan encrypt only the body of the files, or does it obscure the filenames also? I'm looking to avoid the cloud-based robo-suing copyright enforcement bots of the future.