how to use encrypted loop files with a gpg passphrase in Debian

Fast howto (mostly a note for personal use) on what’s needed on Debian to use an encrypted loop:

1. The necessary utilities (patched losetup)
# aptitude install loop-aes-utils
2. The necessary kernel-module
# aptitude install loop-aes-modules-2.6.30-1-686-bigmem
3. Create the keyfile (keep your computer as busy as possible while doing this to increase entropy)
# head -c 2925 /dev/urandom | uuencode -m - | head -n 66 | tail -n 65| gpg --symmetric -a >/path/to/keyfile.gpg
4. Loopfile creation (10Mb)
# dd if=/dev/urandom of=/my-encrypted-loop.aes bs=1k count=10000
5. Initialize loopfile
# losetup -K /path/to/keyfile.gpg -e AES256 /dev/loop5 /home/username/crypto-loop.img
6. Format loopfile
# mke2fs /dev/loop5
7. Delete loop device
# losetup -d /dev/loop5
8. Create mount point for loopfile
# mkdir /mnt/crypto-loop
9. Add entry to fstab

/home/username/crypto-loop.img /mnt/crypt-loop ext2 defaults,noauto,user,loop=/dev/loop7,encryption=AES256,gpgkey=/path/to/keyfile.gpg 0 0

10. Try mounting the loopfile as user
$ mount /mnt/crypto-loop
11. Check it’s mounted properly
$ mount | grep -i aes

and use it!

P.S. Secure your keyfile.gpg, if it gets lost you won’t _ever_ be able to decrypt what was inside crypto-loop.img!

4 Responses to “how to use encrypted loop files with a gpg passphrase in Debian”

  1. August 29th, 2009 | 00:54
    Using Debian IceWeasel Debian IceWeasel 3.0.12 on Debian GNU/Linux Debian GNU/Linux

    Nice post, thanks for the tip. However, I prefer encfs since it is a bit more platform independent.

  2. August 29th, 2009 | 20:30
    Using WordPress WordPress 2.8.4

    [...] Fast howto (mostly a note for personal use) on what’s needed on Debian to use an encrypted loop: More here [...]

  3. leviathan
    September 3rd, 2009 | 00:11
    Using Mozilla Firefox Mozilla Firefox 3.0.13 on Ubuntu Linux Ubuntu Linux

    oraio file – perasa poly euxarista me TA mount points

  4. September 30th, 2009 | 14:29
    Using WordPress WordPress 2.8.4

    [...] i report a quick HOW-TO from http://www.void.gr , original post is  HERE [...]

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