Loopback file system encryption with kernel-source-2.4.19?

["Jack O'Quin" <joq@io.com>]

I've RTFM'ed and googled all over the place, but still can't build
kernel-source-2.4.19 under Debian Woody with support for loopback file
system encryption.  A lot of what's on the web seems to be out of
date, making it difficult to figure out what's going on.

I managed to install cryptoapi-core-source from testing and build
a 2.4.19 kernel with those modules (plus ALSA).  

But losetup still fails:

  sudo losetup -e blowfish /dev/loop0 ~/.crypto
  Available keysizes (bits): 128 160 192 256 
  Keysize: 256
  Password :xxxxxxxxxxxxx
  
  Password :xxxxxxxxxxxxx
  
  The cipher does not exist, or a cipher module needs to be loaded into the kernel
  ioctl: LOOP_SET_STATUS: Invalid argument

I tried installing cryptoloop-source from testing.  But it only
contains the following patches:

  /usr/src/kernel-patches/all/loop-jari/loop-jari-2.2.20.gz
  /usr/src/kernel-patches/all/loop-jari/loop-jari-2.4.18.gz
  /usr/src/kernel-patches/all/loop-jari/loop-jari-2.4.16.gz

Is this package still needed?  The /usr/share/doc files seem to
indicate that it is.  So, how do I build a patch for 2.4.19?

What am I missing, here?
-- 
  Jack O'Quin
  Austin, Texas, USA