Here’s how you lose everything.
First, someone gets control of your email account. It might be a security vulnerability, or a password attack (note: “tigger”, “angel” and “soccer” are not wise choices), or a password reset, or an inside job.
Please submit your email address. Afterward you will receive an email with a link that will reset your password and securely display the new password to you. The provided link will only work for one hour.
Now they have access to everything you’ve backed up.
CrashPlan talks about their 128-bit Blowfish encryption (standard) or 448-bit CrashPlan+ encryption and how robust that is. As Schneier used to point out before he was overwhelmed by the boredom of it, this is rather besides the point. Their use of the industry standard “password reset by email” process means they’ve built a solid steel door on a house made of rice paper.
CrashPlan also offers a “data password” that encrypts at the client side. So even if someone gets control of your online backup they can’t actually do anything with the data.
Except … Well, CrashPlan’s FAQ dodges around this, but since the encryption is client side they can’t make any changes to whatever you’ve already backed up. So if you want to add, or change, your data password you have to wipe your online backup and start over. If you change it, but don’t start over, you better keep your old and new password since data may be encrypted with one or the other. In my home a full family CrashPlan offline backup takes about 4 weeks, so this is not a trivial change.
Note that I’m using CrashPlan as my example here because they’re the best in the offline consumer backup business, and they are the only offline backup plan I’ve considered. They just have the usual problem with their password reset procedure.
How could CrashPlan make the best of a bad situation? Well, in the unlikely event that they read this, they can research higher quality reset procedures (not #$!$!$ security questions). Those reset procedures often involve two factor authentication procedures, such as the procedure myOpenID almost got right. They involve more expense, so it would be reasonable to for CrashPlan to charge extra for a higher quality security service. They really don’t need more encryption, they need better reset controls.
In the meanwhile this problem has tipped me away, for now, from using offline backup. I’ll continue to rely on physical drive rotation for offline security and I may make use of CrashPlan’s (free, unfortunately – I distrust the longevity of free things) ‘backup to friend plan.
Update 2/4/10: For more on CrashPlan.
Update 5/17/10: Matthew Dornquast of ChrashPlan replies in comments.