Echoes Corsac.net - Echoes camshot
mercredi 14 mars 2007 (1 post)
Theses days, I've been looking for a way to have crypto-containers in Debian. I wanted something easy to use, easy to move but still quite secure, which wouldn't require root access to the box, and as an option could use my gpg key.

I looked closely at two projects:

* cryptsetup/luks

The nice thing is that you only have one file containing all your crypted filesystem, it uses the Linux unified key management system (luks), and you are able to use a gpg key to crypt the data. I didn't tried it yet, because there are some drawbacks which I find really important. It uses multiple commands for every operations (creating the container, mounting and unmounting it).

For creating the crypto container you need to:
- create the file
- use it as a loop device (root access)
- initialize the container
- open the container
- create a filesystem on it
- mount it

Each time you want to mount it, you need to:
- create the loop device from the file
- open the container
- mount it

It surely can be wrapped, but that may be difficult to deploy. And you need root access for all operations (you can mount/umount without it using fstab, pmount or things like that, but still it's using privilegied access). And the major drawback, I think, is that the container size is fixed. You choose it when you create the initial file which you'll mount as a loop device. I don't know if there's a way to extend it after creating crypto-container, but anyway it'll need to be manual.

* encfs

encfs is fuse-based, so it doesn't require anything, beside fuse support in the kernel and your user belonging to fuse group. No need to root access nor anything. You create the container with only one command, then mount or umount it with only one command too. You can add and remove files from the container without asking yourself about disk usage or something, because the container is "expanded" (see after) when you add files, automatically.

There are two drawbacks in encfs, for me:
- crypto-container isn't a file, but a folder, with files and folders using crypted filenames but real size. (more or less, because you can use options to modify it but you won't hide a 20MB file for example). It's less secure than a one-file crypto-container where you can't determine how many files there are in it (and with crypsetup/luks, you won't be able to determine how much space is used in the container as the size is fixed anyway). It's less easy to move around, put on an usb key or transmit. You can tar it, yes, but you lose the comfort.
- you can't use a gpg key

In the end, I guess I'd like something like .dmg OSX Disk Images, which can be encrypted. They are really easy to use, as far as I could have seen. Maybe not so secure, but this is a bruteforce attack against master password (1024 bits RSA key), not against 128bits aes key of the container.

Anyway, I've setup an encfs folder here, but am still looking for something wich would improve the situation.

Corsac@23:14:43 (Debian)

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