cryptsetup with automount

[Farkas Levente <lfarkas@bppiac.hu>]

hi,
may be it seems to be offtopic, but first i have to describe the problem
or just jump to the QUESTION.
recently i try to use encrypted filesystem on linux. now i'd not like
into the detail, but it seems currently the best solution is LUKS on
dm-crypt (http://luks.endorphin.org/dm-crypt). the whole thing is well
documented:
http://www.flyn.org/easycrypto/easycrypto.html
http://www.saout.de/tikiwiki/tiki-index.php?page=EncryptedDeviceUsingLUKS
and working for block device and file container.
the only problem you always need to be root:-(
what i would like to do, setup everything as root (create luks partition
is a file in this way eg):
--------------------------------
dd if=/dev/urandom of=/home/lfarkas/.private bs=1M count=2048
losetup /dev/loop0 /home/lfarkas/.private
cryptsetup luksFormat /dev/loop0
cryptsetup luksOpen /dev/loop0 private
mkfs.ext3 /dev/mapper/private
mount /dev/mapper/private /home/lfarkas/private
umount /home/lfarkas/private
cryptsetup luksClose private
losetup -d /dev/loop0
--------------------------------
and after then i'd like to allow user lfarkas to mount his own file and
use it. ie:
--------------------------------
losetup /dev/loop0 /home/lfarkas/.private
cryptsetup luksOpen /dev/loop0 private
mount /dev/mapper/private /home/lfarkas/private
umount /home/lfarkas/private
cryptsetup luksClose private
losetup -d /dev/loop0
--------------------------------
and here comes the problems:
- losetup can used only by root,
- cryptsetup luksOpen/luksClose can used only by root,
- there is a modified mount at :
http://people.redhat.com/kzak/util-linux-cryptsetup/
which should have to allow this with:
mount /home/lfarkas/.private /home/lfarkas/private -t ext3 -o crypt,loop
it always give me:
--------------------------------
mount: wrong fs type, bad option, bad superblock on /dev/loop0,
       missing codepage or other error
       In some cases useful info is found in syslog - try
       dmesg | tail  or so
--------------------------------
while at the and of dmesg:
--------------------------------
VFS: Can't find ext3 filesystem on dev loop0.
--------------------------------

================== QUESTION ====================
so what comes into my mind, may be i can use autofs. can i define some
scripts which are run:
- before the mount
- after the umount
i can use program map and run losetup and cryptsetup luksOpen in it (can
i do so?) and this run by the kernel so run as root. but how can i give
the password of key file in this case? and is there any way to define
post umount script?
yours.

-- 
  Levente                               "Si vis pacem para bellum!"