implement it for nCipher hardware. The interface in itself should be
clear enough, but the nCipher implementation is currently not the
best when it comes to getting a passphrase from the user. However,
getting it better is a little hard until a better user interaction
method is create.
Also, use the possibility in req, so we can start to create CSR's with
keys from the nForce box.
WARNING: I've made *no* tests yet, mostly because I didn't implement
this on the machine where I have an nForce box to play with. All I
know is that it compiles cleanly on Linux...