1.\" $NetBSD: cgd.4,v 1.14 2010/04/14 13:06:45 wiz Exp $ 2.\" 3.\" Copyright (c) 2002, 2003 The NetBSD Foundation, Inc. 4.\" All rights reserved. 5.\" 6.\" This code is derived from software contributed to The NetBSD Foundation 7.\" by Roland C. Dowdeswell. 8.\" 9.\" Redistribution and use in source and binary forms, with or without 10.\" modification, are permitted provided that the following conditions 11.\" are met: 12.\" 1. Redistributions of source code must retain the above copyright 13.\" notice, this list of conditions and the following disclaimer. 14.\" 2. Redistributions in binary form must reproduce the above copyright 15.\" notice, this list of conditions and the following disclaimer in the 16.\" documentation and/or other materials provided with the distribution. 17.\" 18.\" THIS SOFTWARE IS PROVIDED BY THE NETBSD FOUNDATION, INC. AND CONTRIBUTORS 19.\" ``AS IS'' AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED 20.\" TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR 21.\" PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE FOUNDATION OR CONTRIBUTORS 22.\" BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR 23.\" CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF 24.\" SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS 25.\" INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN 26.\" CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) 27.\" ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE 28.\" POSSIBILITY OF SUCH DAMAGE. 29.\" 30.Dd April 14, 2010 31.Dt CGD 4 32.Os 33.Sh NAME 34.Nm cgd 35.Nd cryptographic disk driver 36.Sh SYNOPSIS 37.Cd "pseudo-device cgd" Op Ar count 38.Sh DESCRIPTION 39The 40.Nm 41driver provides the capability of encrypting blocks on their way 42to and from a disk or partition. 43.Pp 44In order to compile support for the 45.Nm 46into your kernel, you must add the driver to your kernel configuration 47file. 48To do this, add a line similar to: 49.Bd -unfilled -offset indent 50pseudo-device cgd 4 # cryptographic disk driver 51.Ed 52.Pp 53The count argument defines how many 54.Nm Ns 's 55may be configured at a time. 56.Ss Encryption Algorithms 57Currently the following cryptographic algorithms are supported: 58.Bl -tag -width indentxxxxxxx 59.It aes-cbc 60AES in CBC mode. 61AES uses a 128 bit blocksize and can accept keys of 62length 128, 192, or 256. 63The default key length is 128. 64.It 3des-cbc 65Triple DES in CBC mode. 66Triple DES uses a 64 bit blocksize and is 67performed in EDE3 mode with a 168 bit key. 68The key passed to the kernel 69is 192 bits but the parity bits are ignored. 70.It blowfish-cbc 71Blowfish in CBC mode. 72Blowfish uses a 64 bit blocksize and can accept keys between 40 and 73448 bits in multiples of 8. 74It is strongly encouraged that keys be at least 128 bits long. 75There are no performance advantages of using shorter keys. 76The default key length is 128 bits. 77.El 78.Ss IV Methods 79Currently, the following IV Methods are supported: 80.Bl -tag -width encblkno1 81.It encblkno1 82This method encrypts the block number of the physical disk block once with 83the cipher and key provided and uses the result as the IV for CBC mode. 84This method should ensure that each block has a different IV and that the IV 85is reasonably unpredictable. 86This is the default method used by 87.Xr cgdconfig 8 88when configuring new 89.Nm Ns 's . 90.It encblkno8 91This is the original IV method used by 92.Nm 93and provided for backward compatibility. 94It repeatedly encrypts the block number of the physical disk block 95eight times and uses the result as the IV for CBC mode. 96This method should ensure that each block has a different IV and that the IV 97is reasonably unpredictable. 98The eightfold encryption was not intended and causes a notable 99performance loss with little (if any) increase in security over a 100single encryption. 101.El 102.Ss IOCTLS 103A 104.Nm 105responds to all of the standard disk 106.Xr ioctl 2 107calls defined in 108.Xr sd 4 , 109and also defines the following: 110.Bl -tag -width CGDIOCSET 111.It CGDIOCSET 112configure the 113.Nm . 114This 115.Xr ioctl 2 116sets up the encryption parameters and points the 117.Nm 118at the underlying disk. 119.It CGDIOCCLR 120unconfigures the 121.Nm . 122.El 123.Pp 124These 125.Xr ioctl 2 Ns 's 126and their associated data structures are defined in 127.Pa /usr/include/dev/cgdvar.h . 128.Sh WARNINGS 129It goes without saying that if you forget the passphrase that you used 130to configure a 131.Nm , 132then you have irrevocably lost all of the data on the disk. 133Please ensure that you are using an appropriate backup strategy. 134.Sh FILES 135.Bl -tag -width indentxxxxxxxxxxx 136.It /dev/{,r}cgd* 137.Nm 138device special files. 139.El 140.Sh SEE ALSO 141.Xr config 1 , 142.Xr ioctl 2 , 143.Xr sd 4 , 144.Xr cgdconfig 8 , 145.Xr MAKEDEV 8 146.Rs 147.%A Roland C. Dowdeswell 148.%A John Ioannidis 149.%T The CryptoGraphic Disk Driver 150.%I USENIX Association 151.%B Proceedings of the FREENIX Track: 2003 USENIX Annual Technical Conference 152.%P 179-186 153.%D June 9-14, 2003 154.%U http://www.usenix.org/event/usenix03/tech/freenix03/full_papers/dowdeswell/dowdeswell.pdf 155.Re 156.Sh HISTORY 157The 158.Nm 159driver was written by Roland C. Dowdeswell for 160.Nx . 161The 162.Nm 163driver originally appeared in 164.Nx 2.0 . 165