hard drive encryption

There’s a lot of buzz around hard drive encryption. If you’re not a “technical person” you might have the wrong idea about what it is and how it helps. This has nothing to do with the cloud; it’s a method you can improve the security of your computer or mobile device from a local attacker who has access to it.

The gist of full disk encryption is simple: it improves local device security, but it isn’t a magic bullet.

WHAT’S THE THREAT MODEL?

When analyzing how good or bad a security solution is, the first thing we need to look at is its threat model, or what’s it is supposed to protect us from.

In the case of disk encryption, the threat model is basically this: protect from unauthorized access once in possession of the actual drive.

Pay attention to the bold text in that last sentence; it is really important. At first it was thought disk encryption would protect users from situations where a computer is suspended when the attacker has access, but the security community have known for a while that’s not really the case. Hard disk encryption protects you as long as you have turned off your computer and waited a couple of minutes so that the RAM is clear of any “residual data.”

If you skipped the link above please take a few minutes to give it a look. It makes hacking in the movies look not too far from what happens in the real world.

ON LAPTOPS

So, back to the practical bits:

ON PHONES

If you’re an Android user, you can follow this guide and make sure you have the latest Android version available for your phone. If you are an iOS user, you can follow this guide.

HIDDEN VOLUMES?

There’s a feature in some encryption software called “hidden volumes.” The idea is that by exploiting some encryption magic you can have a virtually infinite number of hidden volumes on your drive. They will look like gibberish, but since you hold the key, you can unlock them.

The goal of this feature is to allow you to give the password for a visible volume with unimportant data if you are forced to give up your encryption key, and still leave your sensitive data in a hidden volume that has a different key. (Think of a journalist who is forced to divulge an encryption key at a hostile border crossing.) This can allow you to comply while still leaving the most sensitive information encrypted.

This isn’t a full-proof solution; the truth is that although the math behind it might be solid but brute force can still be applied and could be successful.

WHY DOESN’T SPIDEROAK ONE ENCRYPT MY HARD DRIVE?

This is beyond the scope of what SpiderOak ONE backup was designed to do. As I said at the start of this post, what you need to look at first thing is the threat model. SpiderOak’s threat model revolves around protecting your backups while they are in transit to our servers and while they are at rest on our servers. We also try to help protect our users’ computers, but that’s not our main goal.

There are a lot of really good tools that answer this threat model such as full disk encryption or local encrypted volumes. Rather than trying to be all things to all people, we’ll always push towards doing one thing really well instead of doing two or more things half way.

THE USUAL WARNING

Full disk encryption is not a one stop solution – it’s just one more barrier an attacker has to circumvent. If you only suspend your laptop, it is still possible for an attacker to get ahold of your encryption keys, but it’s a bit more complex of an attack than without any encryption. There are tools such as iSECPartner’s You’ll Never Take Me Alive! which works on Windows and there also a Mac version that can help improve the basic encryption security by hibernating your laptop instead of just suspending it.

Remember that as with all security measures, full disk encryption can improve your security, but they also might impact the usability of your system. In this case, the small usability tradeoffs are overcome by the greater security that comes from having disk encryption on your computers and mobile devices.