unencrypting on a different system fails

[zeroth]

I've had this happen before: an encrypted volume will unencrypt with losetup and mount fine on the system it was encrypted on, but not another bailing with "must specify file system type" ( usually meaning a bad password, but not the case here ).

the first time this happened was after a large system update, and I was able to chroot from a previous system backup and successfully unencrypt. now I am in the same predicament but have no previous system backup to chroot into.

I've got the encrypted medium (a file) and the correct password and I know the encryption method, but cant unencrypt. so what can I do? whats the issue here?

[zeroth]

heres an interesting bit. with the wrong password I always get this:

mount -oencryption=aes file /mnt/tmp
Password: 
mount: you must specify the filesystem type

but with the correct password, it does this instead:

mount -oencryption=aes file /mnt/tmp
Password: 
mount: wrong fs type, bad option, bad superblock on /dev/loop1,
       missing codepage or helper program, or other error
       In some cases useful info is found in syslog - try
       dmesg | tail  or so

and this is what dmesg has to say:

init_special_inode: bogus i_mode (166236) for inode loop0:8
EXT3-fs (loop0): error: invalid journal inode

there are text files on the encrypted medium which would show by doign a `cat /dev/loop0 | strings -n 10` but it shows nothing intelligible. the unencryption is just plain not working like it should...

[zeroth]

another interesting bit, after losetup'ing to loop0 with correct password:

cat /dev/loop0 > tst
file tst
tst: Linux rev 1.0 ext3 filesystem data, UUID=d0830430-7237-4dcd-8b68-c9e35c46916d