After reading this question about how often tmp is cleared, it would be best for our setup if tmp is encrypted. How do I encrypt it?

My fstab looks like this:

proc            /proc           proc    nodev,noexec,nosuid 0       0

/dev/mapper/vg_doulos-root /               ext4    errors=remount-ro 0       1

# /boot was on /dev/sda1 during installation

UUID=205a1a54-7dfa-45a6-a7e3-4a7234b3a473 /boot           ext4    defaults        0   2

/dev/mapper/vg_doulos-home /home           ext4    defaults        0       2

/dev/mapper/vg_doulos-tmp /tmp            ext4    defaults        0       2

# swap was on /dev/sda2 during installation

#UUID=705e9f69-bf95-4d44-9119-c40076d10333 none            swap    sw              0  0

/dev/mapper/cryptswap1 none swap sw 0 0

crypttab:

# <target name> <source device>         <key file>      <options>

cryptswap1 /dev/sda2 /dev/urandom swap,cipher=aes-cbc-essiv:sha256

Is it sufficient to put something like this in crypttab?

crypttmp /dev/mapper/vg_doulos-tmp /dev/urandom

and then this to replace the tmp file entry in fstab?

/dev/mapper/crypttmp /tmp ext4 defaults 0 2