cgd(4)
- NetBSD Manual Pages
CGD(4) NetBSD Kernel Interfaces Manual CGD(4)
NAME
cgd - cryptographic disk driver
SYNOPSIS
pseudo-device cgd [count]
DESCRIPTION
The cgd driver provides the capability of encrypting blocks on their way
to and from a disk or partition.
In order to compile support for the cgd into your kernel, you must add
the driver to your kernel configuration file. To do this, add a line
similar to:
pseudo-device cgd 4 # cryptographic disk driver
The count argument defines how many cgd's may be configured at a time.
Encryption Algorithms
Currently the following cryptographic algorithms are supported:
aes-cbc AES in CBC mode. AES uses a 128 bit blocksize and can
accept keys of length 128, 192, or 256. The default key
length is 128.
3des-cbc Triple DES in CBC mode. Triple DES uses a 64 bit block-
size and is performed in EDE3 mode with a 168 bit key.
The key passed to the kernel is 192 bits but the parity
bits are ignored.
blowfish-cbc Blowfish in CBC mode. Blowfish uses a 64 bit blocksize
and can accept keys of length 128.
IV Methods
Currently, the only IV Method supported is encblkno (Encrypted Block Num-
ber). This method encrypts the block number of the physical disk block
with the cipher and key provided and uses that as the IV for CBC mode.
This method should ensure that each block has a different IV and that the
IV is reasonably unpredictable.
IOCTLS
A cgd responds to all of the standard disk ioctl(2) calls defined in
sd(4), and also defines the following:
CGDIOCSET configure the cgd. This ioctl(2) sets up the encryption
parameters and points the cgd at the underlying disk.
CGDIOCCLR unconfigures the cgd.
These ioctl(2)'s and their associated data structures are defined in
/usr/include/dev/cgdvar.h.
WARNINGS
It goes without saying that if you forget the passphrase that you used to
configure a cgd, then you have irrevocably lost all of the data on the
disk. Please ensure that you are using an appropriate backup strategy.
FILES
/dev/{,r}cgd* cgd device special files.
SEE ALSO
ioctl(2), sd(4), MAKEDEV(8), cgdconfig(8), config(8)
HISTORY
The cgd driver was written by Roland C. Dowdeswell for NetBSD. The cgd
driver originally appeared in NetBSD 2.0.
NetBSD 2.0 August 14, 2003 NetBSD 2.0
Powered by man-cgi (2024-03-20).
Maintained for NetBSD
by Kimmo Suominen.
Based on man-cgi by Panagiotis Christias.