The instantiation data passed to the asymmetric key type are expected to be
formatted in some way, and there are several possible standard ways to format
the data.

The two obvious standards are OpenPGP keys and X.509 certificates.  The latter
is especially useful when dealing with UEFI, and the former might be useful
when dealing with, say, eCryptfs.

Further, it might be desirable to provide formatted blobs that indicate
hardware is to be accessed to retrieve the keys or that the keys live
unretrievably in a hardware store, but that the keys can be used by means of
the hardware.

From userspace, the keys can be loaded using the keyctl command, for example,
an X.509 binary certificate:

	keyctl padd asymmetric foo @s <dhowells.pem

or a PGP key:

	keyctl padd asymmetric bar @s <dhowells.pub

or a pointer into the contents of the TPM:

	keyctl add asymmetric zebra "TPM:04982390582905f8" @s

Inside the kernel, pluggable parsers register themselves and then get to...