> I had it working on an OpenBSD 3.4 install, but I've lost my notes and
> the source tree that I hacked to get it working. I do remember fudging
> around with /dev/MAKEDEV and tracking back to allocate a major number
> for the mknod, but then it's all hazy from there.

/dev/crypto support on alpha was added for 3.6. I'd suggest updating
your machine.

If you don't want to update, you need to plus crypto support in
sys/alpha/alpha/conf.c (see rev 1.50) and create the /dev/crypto node
(char major 57 minor 0).