OPEN¶

open <device> <name> --type <device_type>

Opens (creates a mapping with) <name> backed by device <device>.
See cryptsetup-open(8).

CLOSE¶

close <name>

Removes the existing mapping <name> and wipes the key from kernel memory.
See cryptsetup-close(8).

STATUS¶

status <name>

Reports the status for the mapping <name>.
See cryptsetup-status(8).

RESIZE¶

resize <name>

Resizes an active mapping <name>.
See cryptsetup-resize(8).

REFRESH¶

refresh <name>

Refreshes parameters of active mapping <name>.
See cryptsetup-refresh(8).

REENCRYPT¶

reencrypt <device> or --active-name <name> [<new_name>]

Run LUKS device reencryption.
See cryptsetup-reencrypt(8).

OPEN¶

open --type plain <device> <name>
create <name> <device> (OBSOLETE syntax)

Opens (creates a mapping with) <name> backed by device <device>.
See cryptsetup-open(8).

FORMAT¶

luksFormat <device> [<key file>]

Initializes a LUKS partition and sets the initial passphrase (for key-slot 0).
See cryptsetup-luksFormat(8).

OPEN¶

open --type luks <device> <name>
luksOpen <device> <name> (old syntax)

Opens the LUKS device <device> and sets up a mapping <name> after successful verification of the supplied passphrase.
See cryptsetup-open(8).

SUSPEND¶

luksSuspend <name>

Suspends an active device (all IO operations will block and accesses to the device will wait indefinitely) and wipes the encryption key from kernel memory.
See cryptsetup-luksSuspend(8).

RESUME¶

luksResume <name>

Resumes a suspended device and reinstates the encryption key.
See cryptsetup-luksResume(8).

ADD KEY¶

luksAddKey <device> [<key file with new key>]

Adds a new passphrase using an existing passphrase.
See cryptsetup-luksAddKey(8).

REMOVE KEY¶

luksRemoveKey <device> [<key file with passphrase to be removed>]

Removes the supplied passphrase from the LUKS device.
See cryptsetup-luksRemoveKey(8).

CHANGE KEY¶

luksChangeKey <device> [<new key file>]

Changes an existing passphrase.
See cryptsetup-luksChangeKey(8).

CONVERT KEY¶

luksConvertKey <device>

Converts an existing LUKS2 keyslot to new PBKDF parameters.
See cryptsetup-luksConvertKey(8).

KILL SLOT¶

luksKillSlot <device> <key slot number>

Wipe the key-slot number <key slot> from the LUKS device.
See cryptsetup-luksKillSlot(8).

ERASE¶

erase <device>
luksErase <device> (old syntax)

Erase all keyslots and make the LUKS container permanently inaccessible.
See cryptsetup-erase(8).

UUID¶

luksUUID <device>

Print or set the UUID of a LUKS device.
See cryptsetup-luksUUID(8).

IS LUKS¶

isLuks <device>

Returns true, if <device> is a LUKS device, false otherwise.
See cryptsetup-isLuks(8).

DUMP¶

luksDump <device>

Dump the header information of a LUKS device.
See cryptsetup-luksDump(8).

HEADER BACKUP¶

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

Stores a binary backup of the LUKS header and keyslot area.
See cryptsetup-luksHeaderBackup(8).

HEADER RESTORE¶

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

Restores a binary backup of the LUKS header and keyslot area from the specified file.
See cryptsetup-luksHeaderRestore(8).

TOKEN¶

token <add|remove|import|export> <device>

Manipulate token objects used for obtaining passphrases.
See cryptsetup-token(8).

CONVERT¶

convert <device> --type <format>

Converts the device between LUKS1 and LUKS2 format (if possible).
See cryptsetup-convert(8).

CONFIG¶

config <device>

Set permanent configuration options (store to LUKS header).
See cryptsetup-config(8).

OPEN¶

open --type loopaes <device> <name> --key-file <keyfile>
loopaesOpen <device> <name> --key-file <keyfile> (old syntax)

Opens the loop-AES <device> and sets up a mapping <name>.
See cryptsetup-open(8).

See also section 7 of the FAQ and loop-AES <http://loop-aes.sourceforge.net> for more information regarding loop-AES.

OPEN¶

open --type tcrypt <device> <name>
tcryptOpen_ <device> <name> (old syntax)

Opens the TCRYPT (a TrueCrypt-compatible) <device> and sets up a mapping <name>.
See cryptsetup-open(8).

DUMP¶

tcryptDump <device>

Dump the header information of a TCRYPT device.
See cryptsetup-tcryptDump(8).

See also TrueCrypt <https://en.wikipedia.org/wiki/TrueCrypt> and VeraCrypt <https://en.wikipedia.org/wiki/VeraCrypt> pages for more information.

Please note that cryptsetup does not use TrueCrypt or VeraCrypt code, please report all problems related to this compatibility extension to the cryptsetup project.

OPEN¶

open --type bitlk <device> <name>
bitlkOpen <device> <name> (old syntax)

Opens the BITLK (a BitLocker-compatible) <device> and sets up a mapping <name>.
See cryptsetup-open(8).

DUMP¶

bitlkDump <device>

Dump the header information of a BITLK device.
See cryptsetup-bitlkDump(8).

Please note that cryptsetup does not use any Windows BitLocker code, please report all problems related to this compatibility extension to the cryptsetup project.

OPEN¶

open --type fvault2 <device> <name>
fvault2Open <device> <name> (old syntax)

Opens the FVAULT2 (a FileVault2-compatible) <device> (usually the second partition on the device) and sets up a mapping <name>.
See cryptsetup-open(8).

DUMP¶

fvault2Dump <device>

Dump the header information of an FVAULT2 device.
See cryptsetup-fvault2Dump(8).

Note that cryptsetup does not use any macOS code or proprietary specifications. Please report all problems related to this compatibility extension to the cryptsetup project.

REPAIR¶

repair <device>

Tries to repair the device metadata if possible. Currently supported only for LUKS device type.
See cryptsetup-repair(8).

BENCHMARK¶

benchmark <options>

Benchmarks ciphers and KDF (key derivation function).
See cryptsetup-benchmark(8).

Passphrase processing for PLAIN mode¶

Note that no iterated hashing or salting is done in plain mode. If hashing is done, it is a single direct hash. This means that low-entropy passphrases are easy to attack in plain mode.

From a terminal: The passphrase is read until the first newline, i.e. '\n'. The input without the newline character is processed with the default hash or the hash specified with --hash. The hash result will be truncated to the key size of the used cipher, or the size specified with -s.

From stdin: Reading will continue until a newline (or until the maximum input size is reached), with the trailing newline stripped. The maximum input size is defined by the same compiled-in default as for the maximum key file size and can be overwritten using --keyfile-size option.

The data read will be hashed with the default hash or the hash specified with --hash. The hash result will be truncated to the key size of the used cipher, or the size specified with -s.

Note that if --key-file=- is used for reading the key from stdin, trailing newlines are not stripped from the input.

If "plain" is used as argument to --hash, the input data will not be hashed. Instead, it will be zero padded (if shorter than the key size) or truncated (if longer than the key size) and used directly as the binary key. This is useful for directly specifying a binary key. No warning will be given if the amount of data read from stdin is less than the key size.

From a key file: It will be truncated to the key size of the used cipher or the size given by -s and directly used as a binary key.

WARNING: The --hash argument is being ignored. The --hash option is usable only for stdin input in plain mode.

If the key file is shorter than the key, cryptsetup will quit with an error. The maximum input size is defined by the same compiled-in default as for the maximum key file size and can be overwritten using --keyfile-size option.

Passphrase processing for LUKS¶

LUKS uses PBKDF to protect against dictionary attacks and to give some protection to low-entropy passphrases (see cryptsetup FAQ).

From a terminal: The passphrase is read until the first newline and then processed by PBKDF2 without the newline character.

From stdin: LUKS will read passphrases from stdin up to the first newline character or the compiled-in maximum key file length. If --keyfile-size is given, it is ignored.

From key file: The complete keyfile is read up to the compiled-in maximum size. Newline characters do not terminate the input. The --keyfile-size option can be used to limit what is read.

Passphrase processing: Whenever a passphrase is added to a LUKS header (luksAddKey, luksFormat), the user may specify how much the time the passphrase processing should consume. The time is used to determine the iteration count for PBKDF2 and higher times will offer better protection for low-entropy passphrases, but open will take longer to complete. For passphrases that have entropy higher than the used key length, higher iteration times will not increase security.

The default setting of one or two seconds is sufficient for most practical cases. The only exception is a low-entropy passphrase used on a device with a slow CPU, as this will result in a low iteration count. On a slow device, it may be advisable to increase the iteration time using the --iter-time option in order to obtain a higher iteration count. This does slow down all later luksOpen operations accordingly.

Incoherent behavior for invalid passphrases/keys¶

LUKS checks for a valid passphrase when an encrypted partition is unlocked. The behavior of plain dm-crypt is different. It will always decrypt with the passphrase given. If the given passphrase is wrong, the device mapped by plain dm-crypt will essentially still contain encrypted data and will be unreadable.

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 the --hash option, if the crypto backend is libgcrypt, then all algorithms supported by the gcrypt library are available. For other crypto backends, some algorithms may be missing.

Notes on passphrases¶

Mathematics can’t be bribed. Make sure you keep your passphrases safe. There are a few nice tricks for constructing a fallback, when suddenly out of the blue, your brain refuses to cooperate. These fallbacks need LUKS, as it’s only possible with LUKS to have multiple passphrases. Still, if your attacker model does not prevent it, storing your passphrase in a sealed envelope somewhere may be a good idea as well.

Notes on Random Number Generators¶

Random Number Generators (RNG) used in cryptsetup are always the kernel RNGs without any modifications or additions to data stream produced.

There are two types of randomness cryptsetup/LUKS needs. One type (which always uses /dev/urandom) is used for salts, the AF splitter and for wiping deleted keyslots.

The second type is used for the volume key. You can switch between using /dev/random and /dev/urandom here, see --use-random and --use-urandom options. Using /dev/random on a system without enough entropy sources can cause luksFormat to block until the requested amount of random data is gathered. In a low-entropy situation (embedded system), this can take a very long time and potentially forever. At the same time, using /dev/urandom in a low-entropy situation will produce low-quality keys. This is a serious problem, but solving it is out of scope for a mere man-page. See urandom(4) for more information.

Authenticated disk encryption (EXPERIMENTAL)¶

Since Linux kernel version 4.12 dm-crypt supports authenticated disk encryption.

Normal disk encryption modes are length-preserving (plaintext sector is of the same size as a ciphertext sector) and can provide only confidentiality protection, but not cryptographically sound data integrity protection.

Authenticated modes require additional space per-sector for authentication tag and use Authenticated Encryption with Additional Data (AEAD) algorithms.

If you configure LUKS2 device with data integrity protection, there will be an underlying dm-integrity device, which provides additional per-sector metadata space and also provide data journal protection to ensure atomicity of data and metadata update. Because there must be additional space for metadata and journal, the available space for the device will be smaller than for length-preserving modes.

The dm-crypt device then resides on top of such a dm-integrity device. All activation and deactivation of this device stack is performed by cryptsetup, there is no difference in using luksOpen for integrity protected devices. If you want to format LUKS2 device with data integrity protection, use --integrity option.

Since dm-integrity doesn’t support discards (TRIM), dm-crypt device on top of it inherits this, so integrity protection mode doesn’t support discards either.

Some integrity modes requires two independent keys (key for encryption and for authentication). Both these keys are stored in one LUKS keyslot.

WARNING: All support for authenticated modes is experimental and there are only some modes available for now. Note that there are a very few authenticated encryption algorithms that are suitable for disk encryption. You also cannot use CRC32 or any other non-cryptographic checksums (other than the special integrity mode "none"). If for some reason you want to have integrity control without using authentication mode, then you should separately configure dm-integrity independently of LUKS2.

Notes on loopback device use¶

Cryptsetup is usually used directly on a block device (disk partition or LVM volume). However, if the device argument is a file, cryptsetup tries to allocate a loopback device and map it into this file. This mode requires Linux kernel 2.6.25 or more recent which supports the loop autoclear flag (loop device is cleared on the last close automatically). Of course, you can always map a file to a loop-device manually. See the cryptsetup FAQ for an example.

When device mapping is active, you can see the loop backing file in the status command output. Also see losetup(8).

LUKS2 header locking¶

The LUKS2 on-disk metadata is updated in several steps and to achieve proper atomic update, there is a locking mechanism. For an image in file, code uses flock(2) system call. For a block device, lock is performed over a special file stored in a locking directory (by default /run/cryptsetup). The locking directory should be created with the proper security context by the distribution during the boot-up phase. Only LUKS2 uses locks, other formats do not use this mechanism.

LUKS on-disk format specification¶

For LUKS on-disk metadata specification see LUKS1 <https://gitlab.com/cryptsetup/cryptsetup/wikis/Specification> and LUKS2 <https://gitlab.com/cryptsetup/LUKS2-docs>.