CRK_MOD_EXP on /dev/crypto

[Christopher Thorpe]

  I've spent a good bit of time looking at source code, forums, and 
archives and am still having trouble.  I'm running an OpenBSD 3.8 
GENERIC#138 i386 server with a Soekris card with hifn drivers.

dmesg says:
hifn0 at pci0 dev 14 function 0 "Hifn 7955/7954" rev 0x00: LZS 3DES ARC4 
MD5 SHA1 RNG AES PK, 32KB dram, irq 11

  The drivers support modular exponentiation, but I'm having trouble 
finding documentation or figuring out how to perform it (it's a "key 
operation") using the interface to /dev/crypto.

  For reference, I looked at Michal Ludvig's port to Linux, and modified 
it to work on OpenBSD; it's located at http://eecs.harvard.edu/~cat/hifn.c 
This works fine, but I'm not having much luck extending it to do the 
modular exponentiation.

  I'm really looking for code examples that do modular exponentation or 
pointers to documentation I'm missing.

  Thanks in advance.

  Chris