Provided by: cryptsetup_1.1.0~rc2-1ubuntu13_i386 bug

NAME

       cryptsetup  -  setup cryptographic volumes for dm-crypt (including LUKS
       extension)

SYNOPSIS

       cryptsetup <options> <action> <action args>

DESCRIPTION

       cryptsetup is used to conveniently setup dm-crypt managed device-mapper
       mappings. For basic dm-crypt mappings, there are five operations.

ACTIONS

       These strings are valid for <action>, followed by their <action args>:

       create <name> <device>

              creates  a  mapping  with  <name>  backed  by  device  <device>.
              <options> can be [--hash, --cipher, --verify-passphrase,  --key-
              file, --key-size, --offset, --skip, --readonly]

       remove <name>

              removes an existing mapping <name>. No options.

       status <name>

              reports the status for the mapping <name>. No options.

       resize <name>

              resizes an active mapping <name>.

              If  --size  (in  sectors)  is  not  specified,  the  size of the
              underlying block device is used.

LUKS EXTENSION

       LUKS, Linux Unified Key Setup, is a standard for hard disk  encryption.
       It  standardizes  a partition header, as well as the format of the bulk
       data.  LUKS  can  manage  multiple  passwords,  that  can  be   revoked
       effectively  and  that  are  protected  against dictionary attacks with
       PBKDF2.

       These are valid LUKS actions:

       luksFormat <device> [<key file>]

              initializes a LUKS partition and sets the  initial  key,  either
              via  prompting  or  via <key file>.  <options> can be [--cipher,
              --verify-passphrase, --key-size, --key-slot].

       luksOpen <device> <name>

              opens the LUKS partition <device> and sets up a  mapping  <name>
              after  successful  verification  of  the  supplied  key material
              (either  via  key  file  by  --key-file,  or   via   prompting).
              <options> can be [--key-file, --readonly].

       luksClose <name>

              identical to remove.

       luksSuspend <name>

              suspends  active device (all IO operations are frozen) and wipes
              encryption key from kernel. Kernel version 2.6.19  or  later  is
              required.

              After  that  operation  you  have to use luksResume to reinstate
              encryption key (and resume device) or luksClose to remove mapped
              device.

              WARNING:  never  try  to  suspend device where is the cryptsetup
              binary itself.

       luksResume <name>

              Resumes suspended device and reinstates encryption key. You will
              need  provide  passphrase  identical  to luksOpen command (using
              prompting or key file).

       luksAddKey <device> [<new key file>]

              add a new key file/passphrase. An  existing  passphrase  or  key
              file  (via  --key-file)  must be supplied. The key file with the
              new material is supplied as a positional argument. <options> can
              be [--key-file, --key-slot].

       luksRemoveKey <device> [<key file>]

              remove supplied key or key file from LUKS device

       luksKillSlot <device> <key slot number>

              wipe  key  with  number <key slot> from LUKS device. A remaining
              passphrase or  key  file  (via  --key-file)  must  be  supplied.
              <options> can be [--key-file].

       luksDelKey <device> <key slot number>

              identical to luksKillSlot, but deprecated action name.

       luksUUID <device>

              print UUID, if <device> has a LUKS header. No options.

       isLuks <device>

              returns true, if <device> is a LUKS partition. Otherwise, false.
              No options.

       luksDump <device>

              dumps the header information of a LUKS partition. No options.

       luksHeaderBackup <device> --header-backup-file <file>

              Stores binary backup of LUKS header and keyslot areas.

              WARNING: Please  note  that  with  this  backup  file  (and  old
              passphrase   knowledge)   you  can  decrypt  data  even  if  old
              passphrase was wiped from real device.

              Also  note  that  anti-forensic  splitter  is  not  used  during
              manipulation with backup file.

       luksHeaderRestore <device> --header-backup-file <file>

              Restores  binary  backup  of  LUKS header and keyslot areas from
              specified file.

              WARNING: All the keyslot  areas  are  overwritten,  only  active
              keyslots  form  backup  file  are  available  after issuing this
              command.

              This command allows restoring header if device  do  not  contain
              LUKS  header  or  if the master key size and data offset in LUKS
              header on device match the backup file.

       For        more        information        about        LUKS,        see
       http://code.google.com/p/cryptsetup/wiki/Specification

OPTIONS

       --hash, -h
              For create action specifies hash to use for password hashing.

              For  luksFormat  action  specifies  hash  used in LUKS key setup
              scheme and volume key digest.

              WARNING:  setting  hash  other  than  sha1  causes  LUKS  device
              incompatible with older version of cryptsetup.

              The  hash  string is passed to libgcrypt, so all hashes accepted
              by gcrypt are supported.   Default  is  "ripemd160"  for  create
              action and "sha1" for luksFormat.

       --cipher, -c
              set  cipher  specification  string. For plain dm-crypt mappings,
              the default is "aes-cbc-plain", for LUKS mappings it’s "aes-cbc-
              essiv:sha256".  For  pre-2.6.10 kernels, use "aes-plain" as they
              don’t understand the new cipher spec strings. To use ESSIV,  use
              "aes-cbc-essiv:sha256".

              For  XTS mode, kernel version 2.6.24 or more recent is required.
              Use "aes-xts-plain" cipher specification and set key size to 256
              (or 512) bits (see -s option).

       --verify-passphrase, -y
              query  for  passwords  twice.  Useful  when creating a (regular)
              mapping for the first time, or when running luksFormat.

       --key-file, -d
              use file as key material. With LUKS, key  material  supplied  in
              key  files  via  -d are always used for existing passphrases. If
              you want to set a new key via a key file,  you  have  to  use  a
              positional arg to luksFormat or luksAddKey.

              If  the  key  file is "-", stdin will be used. This is different
              from how cryptsetup usually reads from stdin. See section  NOTES
              ON PASSWORD PROCESSING for more information.

       --master-key-file
              Use  pre-generated  master key stored in file. For luksFormat it
              allows LUKS header reformatting with the same master key (if all
              other  parameters  are  the same existing encrypted data remains
              intact).

              For luksAddKey it allows adding new passphrase with only  master
              key knowledge.

       --key-slot, -S
              For  LUKS  operations that add key material, this options allows
              to you specify which key slot is selected for the new key.  This
              option can be used for luksFormat and luksAddKey.

       --key-size, -s
              set  key  size  in bits. Has to be a multiple of 8 bits. The key
              size is limited by the used cipher. See output  of  /proc/crypto
              for  more information. Can be used for create or luksFormat, all
              other LUKS actions will  use  key-size  specified  by  the  LUKS
              header. Default is 128 for luksFormat and 256 for create.

              For  luksOpen this option specifies number of bits read from the
              key-file (default is exhaustive read from key-file).

       --size, -b
              force the size of the underlying device in sectors.  This option
              is only relevant for create and resize action.

       --offset, -o
              start  offset  in  the  backend  device.   This  option  is only
              relevant for create action.

       --skip, -p
              how many sectors of the encrypted data to skip at the beginning.
              This  is  different from the --offset options with respect to IV
              calculations. Using --offset will shift the  IV  calculation  by
              the same negative amount. Hence, if --offset n, sector n will be
              the first sector on the mapping with IV 0.  Using  --skip  would
              have  resulted in sector n being the first sector also, but with
              IV n.  This option is only relevant for create action.

       --readonly
              set up a read-only mapping.

       --iter-time, -i
              The  number  of  milliseconds  to  spend  with  PBKDF2  password
              processing.  This option is only relevant to the LUKS operations
              as luksFormat or luksAddKey.

       --batch-mode, -q
              Do not ask for confirmation. Use with care! This option is  only
              relevant    for   luksFormat,   luksAddKey,   luksRemoveKey   or
              luksKillSlot.

       --timeout, -t
              The number of seconds to wait before  timeout.  This  option  is
              relevant  every time a password is asked, like create, luksOpen,
              luksFormat  or  luksAddKey.  It  has  no  effect  if   used   in
              conjunction with --key-file.

       --tries, -T
              How  often  the  input  of the passphrase shall be retried. This
              option is relevant every time a password is asked, like  create,
              luksOpen, luksFormat or luksAddKey. The default is 3 tries.

       --align-payload=value
              Align  payload  at  a  boundary  of value 512-byte sectors. This
              option is relevant for luksFormat.  If your block  device  lives
              on  a  RAID, it is useful to align the filesystem at full stripe
              boundaries so it can take advantage of the RAID’s geometry.  See
              for instance the sunit and swidth options in the mkfs.xfs manual
              page. By default, the payload is aligned at an  8  sector  (4096
              byte) boundary.

       --version
              Show the version.

NOTES ON PASSWORD PROCESSING

       From  a  file descriptor or a terminal: Password processing is new-line
       sensitive, meaning the reading will stop after encountering \n. It will
       process  the  read  material (without newline) with the default hash or
       the hash given by --hash. After hashing, it will be cropped to the  key
       size given by -s.

       From  stdin: Reading will continue until EOF (so using e.g. /dev/random
       as stdin will not work), with the trailing newline stripped. After that
       the read data will be hashed with the default hash or the hash given by
       --hash and the result will be cropped to the keysize given  by  -s.  If
       "plain"  is used as an argument to the hash option, the input data will
       not be hashed.  Instead, it will be zero padded (if  shorter  than  the
       keysize) or truncated (if longer than the keysize) and used directly as
       the key. No warning will be given if the amount of data read from stdin
       is less than the keysize.

       From  a  key file: It will be cropped to the size given by -s. If there
       is insufficient key material in the key file, cryptsetup will quit with
       an error.

       If  --key-file=-  is  used  for reading the key from stdin, no trailing
       newline is stripped from the input.  Without  that  option,  cryptsetup
       strips trailing newlines from stdin input.

NOTES ON PASSWORD PROCESSING FOR LUKS

       LUKS  uses PBKDF2 to protect against dictionary attacks (see RFC 2898).

       LUKS will always do an exhaustive password reading. Hence, password can
       not  be  read from /dev/random, /dev/zero or any other stream that does
       not terminate.

       LUKS saves the processing  options  when  a  password  is  set  to  the
       respective  key  slot.  Therefore, no options can be given to luksOpen.
       For any password creation action (luksAddKey, or luksFormat), the  user
       may  specify  how much the time the password processing should consume.
       Increasing the time will lead to a more secure password, but also  will
       take  luksOpen longer to complete. The default setting of one second is
       sufficient for good security.

INCOHERENT BEHAVIOUR FOR INVALID PASSWORDS/KEYS

       LUKS checks for a valid password or key when an encrypted partition  is
       unlocked.  Thus the luksOpen action fails with invalid password or key,
       contrary to the plain dm-crypt create action.

NOTES ON SUPPORTED CIPHERS, MODES, HASHES AND KEY SIZES

       The available combinations of ciphers,  modes,  hashes  and  key  sizes
       depend  on  kernel  support.  See  /proc/crypto for a list of available
       options. You might need to load additional  kernel  crypto  modules  in
       order to get more options.

       For  --hash  option  all  algorithms  supported  by  gcrypt library are
       available.

NOTES ON PASSWORDS

       Mathematics can’t be bribed. Make sure you keep  your  passwords  safe.
       There  are a few nice tricks for constructing a fallback, when suddenly
       out of (or after being) blue, your brain refuses  to  cooperate.  These
       fallbacks  are  possible  with LUKS, as it’s only possible with LUKS to
       have multiple passwords.

AUTHORS

       cryptsetup is written by Christophe Saout <christophe@saout.de>
       LUKS    extensions,    and    man    page    by    Clemens    Fruhwirth
       <clemens@endorphin.org>

COMPATABILITY WITH OLD SUSE TWOFISH PARTITIONS

       To  read  images  created with SuSE Linux 9.2’s loop_fish2 use --cipher
       twofish-cbc-null -s 256 -h sha512, for images created with  even  older
       SuSE Linux use --cipher twofish-cbc-null -s 192 -h ripemd160:20

DEPRECATED ACTIONS

       reload <name> <device>

              modifies  an  active mapping <name>. Same options as for create.
              WARNING: Do not use this for LUKS devices, as the semantics  are
              identical  to  the create action, which are totally incompatible
              with the LUKS key setup.

              This action is deprected because it proved to be rarely  useful.
              It  is  uncommon to change the underlying device, key, or offset
              on the fly. In case, you really want to do this,  you  certainly
              know  what  you  are  doing and then you are probably better off
              with the swiss knive tool for device mapper, namely dmsetup.  It
              provides you with the same functionality, see dmsetup reload.

       luksDelKey <device> <key slot number>

              identical  to  luksKillSlot,  but  deprecated  action name. This
              option was renamed, as we  introduced  luksRemoveKey,  a  softer
              method for disabling password slots. To make a clear distinction
              that luksDelKey was more brutal than luksRemoveKey

REPORTING BUGS

       Report bugs to <dm-crypt@saout.de>.

COPYRIGHT

       Copyright © 2004 Christophe Saout
       Copyright © 2004-2006 Clemens Fruhwirth

       This is free software; see the source for copying conditions.  There is
       NO  warranty;  not even for MERCHANTABILITY or FITNESS FOR A PARTICULAR
       PURPOSE.

SEE ALSO

       dm-crypt website, http://www.saout.de/misc/dm-crypt/

       LUKS website, http://code.google.com/p/cryptsetup/

       dm-crypt TWiki, http://www.saout.de/tikiwiki/tiki-index.php