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Basics of Cryptographic Filesystems
mix_master_mike writes "Found a good article over at security focus: cryptographic filesystems: design and implementation. Nice piece on this level of security that isn't being used very effectively in the industry."
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I know I'm going off on a tangent, but I think it's relevant... One of the big problems with PC security is swap space. Unencrypted data often finds its way onto the disk when memory space is swapped out. The simplest solution would be to just load the system up with a huge amount of RAM and disable swapping entirely, but that can get expensive.
Are there any crypto schemes designed specifically for use on swap files and volumes? They'd need to be blazingly fast so as not to slow the machine down, but would also have to be strong enough to protect anything that gets dumped to the drive. Maybe a big (2 meg plus) hash table generated randomly on boot, with a few extra operations to keep block comparisons from working?
Maybe its largely unused because servers etc which are the biggest use of "the industry" aswell as workstations are supposed to be physically secure anyways and when in use the crypto-filesystems would be running unencrypted.
Crypted filesystems have their uses but they arent as many as one would imagine. Laptops for instance should have it by default. That should be remedied. But as long as there arent crypto offloading chipsets by default it wont be widely used because of fear to loose speed. Also its not easy enough to use yet..
Wouldn't any OS disallow random programs from accessing the swap files? And when the OS is shut down all the swap files get destroyed.
So then the OS is the only thing that can get to the swap space, where is the security issue? If you're running a hostile OS then you're pretty much fucked anyways.
But I'm no swapspert, so please explain if I'm being stooopid.
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The problem with encrypted filesystems is that, in order to decrypt them, you need some kind of large, ungainly key. Those keys are not justthe kind fo thing you memorize and type in when you boot up the system, so they have to be stored someshere. If they are stored on the disk, in an unencrypted partition, then you no longer are very secure... if they are stored on some kind of physical key, like a USB token, then you are safe if you turn the machine off and you head home, but unless you plan to paged to come into work and plug in your token every time the machine wants to swap Mozilla out of memory, you're probably going to be leaving it plugged in most of the time, and then you are back to leaving the key around for people to grab. And with all of this, you then have the issue of how to recover the system when your usb token burns out or the partition with your key gets corrupted.
While the idea of securing a whole filesystem by using cryptography is a great idea, I have reservations on how it will effect performance. Most secure algorithms tend to be rather slow in operation. Examples include DES, AES, RSA, etc. While this is not to bad when its just decrypting small files, it seems like this could quickly hurt performance with lots of commonly used small files and larger files.
I do understand that many computers sit around idle many times when having to access disk, but it still seems like this will hurt since I will now have to wait for loading and decrypting of the file into memory. Frankly although 2+ GHz of chip speed is nice, I still find times when my computer does not feel fast enough. (Compiling code, editing images, etc).
On the other hand, not everything has to be encrypted, just user files for instance. So it might be possible to find a decent middle ground. However, there still is that problem with the keys laying around on the disk or on usb devices.
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