Cryptographical File System:
Management in an Encrypting File System, Matt Blaze, USENIX Summer 1994 Technical Conference, Boston, MA, June 1994.
Cryptographic File System for Unix, Matt Blaze, Proceedings of the First ACM Conference on Computer and Communications Security, Fairfax, VA, November 1993.
Vendor's product overview:
Network Appliance: http://www.netapp.com/ftp/decru-fileshredding.pdf