encrypted filesystem using losetup

[Hans van Leeuwen <email@hanz.nl>]

Hello,

I am trying to make an encrypted filesystem using losetup with the "-e" 
parameter and twofish.
The problems is that I keep getting the following error:

The cipher does not exist, or a cipher module needs to be loaded into 
the kernel
ioctl: LOOP_SET_STATUS: Invalid argument

Which module is required and how can I apt-get / compile it?
I use debian woody stable with kernel 2.4.18-bf2.4.

Thanks,

Hans