The tpm(4) driver has been added by Sascha Wildner, ported from FreeBSD. What’s it do?
From the man page: “The tpm driver provides support for various trusted platform modules (TPM) that can store cryptographic keys.” Crypto keys stored in hardware, where they are in theory unmangleable, instead of on the disk. At least, that’s my impression after 30 seconds of research.
Matthew Garrett recently posted an introduction to the trusted platform module and what can be done with it.
http://mjg59.dreamwidth.org/24818.html