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AES encrypted file in Debian

I've recently switched from Gentoo to Debian, one of the problems I now have is that I cannot mount an encrypted file that was accessbile under Gentoo. The file is encrypted using aes with a 256 bit key size, but when I try to mount it an error is given. I have the following entry in my fstab and I have insmod'ed the kernel module (in /lib/modules/2.6.8-1-686/kernel/crypto/) and /proc/crypto shows the module correctly, I have also installed "loop-aes-utils" but I'm not entirely sure what that provides which the kernel modules don't!

/etc/fstab

Code:

# Encrypted file

.crypto    Encrypted      ext2    defaults,noauto,loop,encryption=aes-256,user    0 0

Code:

$ cat /proc/crypto

name        : aes

module      : aes_i586

type        : cipher

blocksize    : 16

min keysize  : 16

max keysize  : 32

When running "make menuconfig" I see that the kernel module "AES cipher algorithms (i586)" option allows the following "The AES specifies three key sizes: 128, 192 and 256 bits" so it should be fine.

Code:

$ mount .crypto

Password:

ioctl: LOOP_SET_STATUS: Invalid argument, requested cipher or key length (256 bits) not supported by kernel

Any help appreciated as most of my important data is encrypted in this file so I *really* need to get it back. (In the worst case scenario I still have my Gentoo install on a second disk so I could boot that up and decrypt the files to transfer, but I'd prefer to get the encryption working

Just for some extra info for my previous post, I can successfully mount a file using the loopback interface:

Code:

mount -o ro,loop -t iso9660 /path/to/an/iso/image.iso /mnt/iso/

Worked perfectly, so it is definitely and encryption issue.

As an update to my post I had to resort to running my old Gentoo system to decrypt the files, save them unencrypted and then I could access them in my Debian system.

I have no idea why I couldn't mount the encrypted files in Debian (possibly a version difference?) but I could create an encrypted file in Debian and successfully write to it.

Code:

$ modprobe cryptoloop



$ cd /tmp



$ dd if=/dev/urandom of=test.crypt bs=1M count=10

10+0 records in

10+0 records out

10485760 bytes transferred in 1.634547 seconds (6415087 bytes/sec)



$ losetup -e aes-256 /dev/loop0 test.crypt

Password:



$ mkfs.ext2 /dev/loop0

mke2fs 1.35 (28-Feb-2004)

Filesystem label=

OS type: Linux

Block size=1024 (log=0)

Fragment size=1024 (log=0)

2560 inodes, 10240 blocks

512 blocks (5.00%) reserved for the super user

First data block=1

2 block groups

8192 blocks per group, 8192 fragments per group

1280 inodes per group

Superblock backups stored on blocks:

        8193



Writing inode tables: done

Writing superblocks and filesystem accounting information: done



This filesystem will be automatically checked every 21 mounts or

180 days, whichever comes first.  Use tune2fs -c or -i to override.



$  mount -t ext2 /dev/loop0 crypto/



$ ls -l crypto/

total 12

drwx------  2 root root 12288 Jan 17 17:04 lost+found



$ umount /dev/loop0



$ losetup -d /dev/loop0



$  mount -t ext2 -o loop,encryption=aes-256 test.crypt crypto/

Password:

Works perfectly and I can happily write files and encrypt / decrypt them which is strange because I couldn't decrypt the file from my Gentoo install in my Debian system.

Does anyone have a suggestion for the best way of encrypting files in Linux which are accessible across distros and hopefully should be accessible sometime in the distant future?

That is strange. I wonder why it wouldn't work. :confused:

this is interesting. I'd like to encrypt my /home partition, are you aware of a tutorial for debian on how to do this step by step?

Thanks

Quote:

Originally posted by yanik
this is interesting. I'd like to encrypt my /home partition, are you aware of a tutorial for debian on how to do this step by step?

Thanks

I've tried several different searches on google and couldn't find one that was specific to Debian. Though, I did find the encrypted root FS tutorial. It can easily be modified to accomodate your /home.
http://linuxfromscratch.org/~devine/erfs-howto.html

My thing though, is that I hate hate hate compiling. Fortunately, I found some pre-built loop-aes modules at apt-get.org
www.apt-get.org