Pravdepodobne si mal oddiel zaheslovany pomocou cryptsetup.
Cize najskor si nainstaluj cryptsetup (aptitude install cryptsetup)
a potom si vytvor subor /etc/cryptab
cryptdisk /dev/sdaX none luks
X si daj cislo tvojej particie
po restartovani /etc/init.d/cryptdisk
a zadani svojho hesla
mas svoj ext3 filesystem pristupny v /dev/mapper/cryptdisk
potom staci uz len pridat do fstab takyto riadok, ktory ti pripoji dany disko do adresara data
/dev/mapper/cryptdisk /data ext3 defaults,noatime,errors=remount-ro 0 2
a nakoniec mount -a
a malo by to fungovat 
ak pouzivas lvm tak si tiez najskor nainstaluj
1) dekuju za rady
2) cryptsetup nainstalovan
3) byl to oddil sda3 a heslo, ktere po me chtel, bylo to cho jsem zadaval, takze odhaduju, ze jsem postupoval spravne. (pod /dev/mapper se objevilo, to co melo)
4) mount ... tak ten uz se mi nepodaril.....
mount: wrong fs type, bad option, bad superblock on /dev/mapper/D2,
missing codepage or other error
In some cases useful info is found in syslog - try
dmesg | tail or so
-------------------------------------------- dmesg | tail
[ 831.384516] VFS: Can't find ext3 filesystem on dev dm-0.
[ 847.608760] VFS: Can't find ext3 filesystem on dev dm-0.
[ 921.668622] VFS: Can't find ext3 filesystem on dev dm-0.