# cryptsetup

## NAME



           cryptsetup - utility for configuring and managing encrypted
           storage devices
    


## SYNOPSIS



           **cryptsetup <action> [<options>] <action args>**
    


## DESCRIPTION



           **Cryptsetup** is a utility for configuring and managing full-disk
           encryption on storage devices. It can encrypt block devices (such
           as hard drives or partitions) and containers (disk images stored
           as files).
    
           When you unlock an encrypted volume, **cryptsetup** creates a new
           device mapping that applications can access like any regular
           storage device. The actual encryption and decryption work is
           performed transparently by the kernel’s device-mapper dm-crypt
           driver.
    
           **Cryptsetup** works with two main volume types: plain encrypted
           volumes and LUKS (Linux Unified Key Setup) volumes. Plain volumes
           provide basic encryption, while LUKS volumes include a metadata
           header that enables advanced features like multiple keyslots and
           key management. Additionally, LUKS can be used to manage
           hardware-based encryption on OPAL-capable storage drives.
    
           **Cryptsetup** also provides limited support for volumes created by
           other encryption systems, including **loop-AES** , **TrueCrypt** ,
           **VeraCrypt** , **BitLocker** , and **FileVault2**.
    
           For more information about a specific cryptsetup action, see
           **cryptsetup- <action>**(8), where **< action> **is the name of the
           cryptsetup action.
    
           Cryptsetup devices can be activated during boot through
           crypttab(5), which is part of systemd(1) or other system init
           scripts.
    


## BASIC ACTIONS



           The following are valid actions for all supported device types.
    
       **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).
    


## PLAIN MODE



           Plain dm-crypt encrypts the device sector-by-sector with a single,
           non-salted hash of the passphrase. No checks are performed, and no
           metadata is used. There is no formatting operation. When the raw
           device is mapped (opened), the usual device operations can be used
           on the mapped device, including filesystem creation. Mapped
           devices usually reside in /dev/mapper/<name>.
    
           The following are valid plain device type actions:
    
       **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).
    


## LUKS EXTENSION



           LUKS, the Linux Unified Key Setup, is a standard for disk
           encryption. It adds a standardized header at the start of the
           device, a keyslot area directly behind the header and the bulk
           data area behind that. The whole set is called a 'LUKS container'.
           The device that a LUKS container resides on is called a 'LUKS
           device'. For most purposes, both terms can be used
           interchangeably.
    
           LUKS can manage multiple passphrases that can be individually
           revoked or changed. Each passphrase uses an individual keyslot
           containing a volume key for data encryption. Keyslots can be
           securely scrubbed from persistent media due to the use of
           anti-forensic stripes. Passphrases are protected against
           brute-force attacks by the Password-Based Key Derivation Function
           (PBKDF). A passphrase stored in a file is called a key file. The
           only difference between a passphrase and a key file is that a key
           file can contain binary data. Both are processed the same.
    
           LUKS version 1 (or LUKS1) is the original metadata format, while
           LUKS2 is a new version that allows additional extensions like
           different PBKDF algorithms or authenticated encryption. You can
           format the device with a specific LUKS version with **--type luks1**
           or **--type luks2** in the **luksFormat** command. Normally, you do not
           need to specify any version as it is recognized automatically. The
           default format is LUKS2.
    
           The **< device> **parameter can also be specified by a LUKS UUID in the
           format UUID=<uuid>.
    
           The LUKS header can be detached from data (stored separately). To
           specify a detached header, the --header parameter can be used in
           all LUKS commands and always takes precedence over the positional
           **< device> **parameter.
    
           The following are valid LUKS actions:
    
       **FORMAT**
           **luksFormat <device> [<key file>]**
    
           Initializes a LUKS partition and sets the initial passphrase (for
           keyslot 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> <number>**
    
           Wipe the keyslot with the <number> 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).
    


## LOOP-AES EXTENSION



           Cryptsetup supports mapping a loop-AES encrypted partition using a
           compatibility mode.
    
       **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.
    


## TCRYPT (TRUECRYPT AND VERACRYPT COMPATIBLE) EXTENSION



           Cryptsetup supports mapping of TrueCrypt, tcplay, or VeraCrypt
           encrypted partitions using a native Linux kernel API. Header
           formatting and TCRYPT header change are not supported; cryptsetup
           never changes the TCRYPT header on-device.
    
           TCRYPT extension requires the kernel userspace crypto API to be
           available. If you are configuring the kernel yourself, enable
           "User-space interface for symmetric key cipher algorithms" in
           "Cryptographic API" section (CRYPTO_USER_API_SKCIPHER .config
           option).
    
           Because the TCRYPT header is encrypted, you must always provide a
           valid passphrase and keyfiles.
    
           Cryptsetup should recognize all header variants, except legacy
           cipher chains using LRW encryption mode with a 64-bit encryption
           block (namely, Blowfish in LRW mode is not recognized; this is a
           limitation of the kernel crypto API).
    
           VeraCrypt is an extension of TrueCrypt with an increased iteration
           count, so unlocking can take quite a lot of time.
    
           To open a VeraCrypt device with a custom Personal Iteration
           Multiplier (PIM) value, use either the --veracrypt-pim PIM option
           to directly specify the PIM on the command line or use
           --veracrypt-query-pim to be prompted for the PIM.
    
           The PIM value affects the number of iterations applied during key
           derivation. Please refer to PIM
           <https://veracrypt.io/en/Personal%20Iterations%20Multiplier%20(PIM).html>
           for more detailed information.
    
           If you need to disable VeraCrypt device support, use
           --disable-veracrypt option.
    
           Activation with **tcryptOpen** is supported only for cipher chains
           using LRW or XTS encryption modes.
    
           The **tcryptDump** command should work for all recognized TCRYPT
           devices and doesn’t require superuser privilege.
    
           To map the system device (device with boot loader where the whole
           encrypted system resides), use --tcrypt-system option. Please read
           specific info in cryptsetup-tcryptOpen(8) --tcrypt-system option
           section as mapping system-encrypted device is tricky.
    
           To use a hidden header (and map hidden device, if available), use
           --tcrypt-hidden option.
    
           To explicitly use the backup (secondary) header, use
           --tcrypt-backup option.
    
           There is no protection for a hidden volume if the outer volume is
           mounted. The reason is that if there were any protection, it would
           require some metadata describing what to protect in the outer
           volume, and the hidden volume would become detectable.
    
       **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.
    


## BITLK (WINDOWS BITLOCKER COMPATIBLE) EXTENSION



           Cryptsetup supports mapping of BitLocker and BitLocker to Go
           encrypted partitions using a native Linux kernel API. Header
           formatting and BITLK header changes are not supported; cryptsetup
           never changes the BITLK header on-device.
    
           BITLK extension requires the kernel userspace crypto API to be
           available (for details, see the TCRYPT section).
    
           Cryptsetup should recognize all BITLK header variants, except the
           legacy header used in Windows Vista systems and partially
           decrypted BitLocker devices. Activation of legacy devices
           encrypted in CBC mode requires at least a Linux kernel version
           5.3, and for devices using the Elephant diffuser, kernel 5.6.
    
           The **bitlkDump** command should work for all recognized BITLK devices
           and doesn’t require superuser privilege.
    
           For unlocking with the **open** , a password, a recovery passphrase, or
           a startup key must be provided.
    
           Additionally, unlocking using the volume key is supported. You
           must provide BitLocker Full Volume Encryption Key (FVEK) using the
           --volume-key-file option. The key must be decrypted and without
           the header (only 128/256/512 bits of key data depending on the
           used cipher and mode).
    
           Other unlocking methods (TPM, SmartCard) are not supported.
    
       **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.
    


## FVAULT2 (APPLE MACOS FILEVAULT2 COMPATIBLE) EXTENSION



           Cryptsetup supports the mapping of FileVault2 (FileVault2
           full-disk encryption) by Apple for the macOS operating system
           using a native Linux kernel API.
    
           Cryptsetup supports only FileVault2 based on Core Storage and HFS+
           filesystem (introduced in MacOS X 10.7 Lion). It does NOT support
           the new version of FileVault based on the APFS filesystem used in
           recent macOS versions.
    
           Header formatting and FVAULT2 header changes are not supported;
           cryptsetup never changes the FVAULT2 header on-device.
    
           FVAULT2 extension requires the kernel userspace crypto API to be
           available (for details, see the TCRYPT section) and a kernel
           driver for the HFS+ (hfsplus) filesystem.
    
           Cryptsetup should recognize the basic configuration for portable
           drives.
    
           The **fvault2Dump** command should work for all recognized FVAULT2
           devices and doesn’t require superuser privilege.
    
           For unlocking with the **open** , a password must be provided. Other
           unlocking methods are not supported.
    
       **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).
    


## SED (SELF ENCRYPTING DRIVE) OPAL EXTENSION



           Cryptsetup supports using native hardware encryption on drives
           that provide an **OPAL** interface, both nested with **dm-crypt** and
           standalone. Passphrases, tokens and metadata are stored using the
           LUKS2 header format, and are thus compatible with any software or
           system that uses LUKS2 (e.g., tokens).
    
           OPAL support requires at least kernel v6.4. Resizing devices is
           not supported.
    
           The --hw-opal can be specified for OPAL + dm-crypt, and
           --hw-opal-only can be specified to use OPAL only, without a
           dm-crypt layer.
    
           Opening, closing and enrolling tokens work the same way as with
           LUKS2 and dm-crypt. The new parameters are only necessary when
           formatting; the LUKS2 metadata will ensure the right setup is
           performed when opening or closing.
    
           If no **subsystem** label is specified, it will be automatically set
           to **HW-OPAL** so that it is immediately apparent when a device uses
           OPAL.
    
       **FORMAT**
           **luksFormat --type luks2 --hw-opal <device> [<key file>]**
    
           Additionally specify --hw-opal-only instead of --hw-opal to avoid
           the dm-crypt layer. Other than the usual passphrase, an admin
           password will have to be specified when formatting the drive’s
           first partition, and will have to be re-supplied when formatting
           any other partition until a factory reset is performed.
    
       **ERASE**
           **erase <device>**
    
           Securely erase a partition or device. Requires admin password.
           Additionally specify --hw-opal-factory-reset for a FULL factory
           reset of the drive, using the drive’s **PSID**(typically printed on
           the label) instead of the admin password.
    
           PSID must be entered without dashes, spaces or underscores.
    
           **WARNING** : A factory reset will cause ALL data on the device to be
           lost, regardless of the partition it is run on, if any, and
           regardless of any LUKS2 header backup.
    


## MISCELLANEOUS ACTIONS



       **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).
    


## PLAIN MODE OR LUKS?



           Unless you understand the cryptographic background well, use LUKS.
           With plain mode, there are a number of possible user errors that
           massively decrease security. While LUKS cannot fix them all, it
           can lessen the impact for many of them.
    


## WARNINGS



           A lot of good information on the risks of using encrypted storage,
           on handling problems and on security aspects can be found in the
           Cryptsetup FAQ. Read it. Nonetheless, some risks deserve to be
           mentioned here.
    
           **Backup:** Storage media die. Encryption has no influence on that.
           Backup is mandatory for encrypted data as well, if the data has
           any worth. See the Cryptsetup FAQ for advice on how to back up an
           encrypted volume.
    
           **Character encoding:** If you enter a passphrase with special
           symbols, the passphrase can change depending on character
           encoding. Keyboard settings can also be changed, which can make
           blind input hard or impossible. For example, switching from some
           ASCII 8-bit variant to UTF-8 can lead to a different binary
           encoding and hence a different passphrase seen by cryptsetup, even
           if what you see on the terminal is exactly the same. It is
           therefore highly recommended to select passphrase characters only
           from 7-bit ASCII, as the encoding for 7-bit ASCII stays the same
           for all ASCII variants and UTF-8.
    
           **LUKS header:** If the header of a LUKS volume gets damaged, all data
           is permanently lost unless you have a header backup. If a keyslot
           is damaged, it can only be restored from a header backup or if
           another active keyslot with a known passphrase is undamaged. This
           risk is the result of a trade-off between security and safety, as
           LUKS is designed for fast and secure wiping by just overwriting
           the header and keyslot area.
    
           **Previously used partitions:** If a partition was previously used, it
           is a very good idea to wipe filesystem signatures, data, etc.,
           before creating a LUKS or plain dm-crypt container. For a quick
           removal of filesystem signatures, use wipefs(8) with the --all
           option. Note that it does not remove data; it only invalidates
           known format signatures. For a full wipe, overwrite the whole
           partition before creating a container. If you do not know how to
           do that, the cryptsetup FAQ describes several options.
    


## EXAMPLES



           Example 1: Create LUKS 2 container on block device /dev/sdX.
               sudo cryptsetup --type luks2 luksFormat /dev/sdX
    
           Example 2: Add an additional passphrase to keyslot 5.
               sudo cryptsetup luksAddKey --key-slot 5 /dev/sdX
    
           Example 3: Create LUKS header backup and save it to a file.
               sudo cryptsetup luksHeaderBackup /dev/sdX --header-backup-file
               /var/tmp/NameOfBackupFile
    
           Example 4: Open LUKS container on /dev/sdX and map it to
           sdX_crypt.
               sudo cryptsetup open /dev/sdX sdX_crypt
    
           **WARNING: The command in example 5 will erase all keyslots.**
               You cannot use your LUKS container afterward anymore unless
               you have a backup to restore.
    
           Example 5: Erase all keyslots on /dev/sdX.
               sudo cryptsetup erase /dev/sdX
    
           Example 6: Restore LUKS header from backup file.
               sudo cryptsetup luksHeaderRestore /dev/sdX
               --header-backup-file /var/tmp/NameOfBackupFile
    


## RETURN CODES



           Cryptsetup returns **0** on success and a non-zero value on error.
    
           Error codes are: **1** wrong parameters, **2** no permission (bad
           passphrase), **3** out of memory, **4** wrong device specified, **5** device
           already exists or device is busy.
    


## NOTES



       **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 the maximum key file size and can be
           overwritten using the --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 an 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.
    
           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 the maximum key file size and can be
           overwritten using the --keyfile-size option.
    
       **Passphrase processing for LUKS**
           **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.
    
           LUKS uses **Password-Based Key Derivation Function**(PBKDF) to
           protect against brute-force attacks and to give some protection to
           low-entropy passphrases (see cryptsetup FAQ). LUKS1 supports the
           PBKDF2 algorithm only, while LUKS2 also supports memory-hard
           Argon2. PBKDFs are configured with costs: how long the iteration
           should run (CPU cost or iteration count), how much memory is used
           (memory cost), and how many parallel processes are used (parallel
           cost). PBKDF2 supports only iteration count. Cryptsetup uses PBKDF
           benchmarking to calculate optimal costs based on the computer
           where the new passphrase is being initialized. If needed, these
           costs can also be overwritten. Note that there are some hardcoded
           limits, for details see **MINIMAL AND MAXIMAL PBKDF COSTS** section in
           --pbkdf option description.
    
           Whenever a passphrase is added to a LUKS header (luksAddKey,
           luksFormat), the user may specify how much 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 the open command 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 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 a keyslot is decrypted.
    
           The behavior of plain dm-crypt is different. It will always unlock
           the device with the passphrase given. If the given passphrase is
           wrong, the device mapped by plain dm-crypt will use the wrong
           encryption key, and the data 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
           to get more options.
    
           Cryptsetup processes many operations outside of the kernel, so the
           configured cryptographic library must also support selected
           algorithms. Some algorithms may be missing as cryptsetup can be
           compiled with various cryptographic backends (libraries).
    
       **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 (RNGs) used in cryptsetup are always the
           kernel RNGs without any modifications or additions to the data
           stream produced.
    
           There are two types of randomness that cryptsetup/LUKS needs. One
           type is used for salts, the AF splitter and for wiping deleted
           keyslots. The second type is used for the volume key.
    
           With recent kernels (Linux kernel 5.6), you do not need to worry
           about selecting RNG (/dev/random or /dev/urandom). In a
           low-entropy situation (embedded system), initialization of the
           kernel RNG can take a very long time, but this happens before
           cryptsetup can even be started. Use _cryptsetup --help_ to show the
           compiled-in default random number generator. See urandom(4) for
           more information.
    
       **Authenticated disk encryption (EXPERIMENTAL)**
           Normal disk encryption modes are length-preserving (the plaintext
           sector is the same size as a ciphertext sector) and can provide
           only confidentiality protection, not cryptographically sound data
           integrity protection.
    
           Authenticated modes require additional space per-sector for the
           authentication tag and use Authenticated Encryption with
           Additional Data (AEAD) algorithms.
    
           If you configure a LUKS2 device with data integrity protection,
           there will be an underlying dm-integrity device, which provides
           additional per-sector metadata space and data journal protection
           to ensure atomicity of data and metadata updates. 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 a LUKS2
           device with data integrity protection, use --integrity option (see
           cryptsetup-luksFormat(8)).
    
           Albeit Linux kernel 5.7 added TRIM support for standalone
           dm-integrity devices, cryptsetup(8) can’t offer support for
           discards (TRIM) in authenticated encryption mode, because the
           underlying dm-crypt kernel module does not support this
           functionality when dm-integrity is used as auth tag space
           allocator (see --allow-discards in cryptsetup-open(8)).
    
           Some integrity modes require two independent keys (a key for
           encryption and authentication). Both these keys are stored in one
           LUKS keyslot.
    
           Support for authenticated modes is experimental, and only some
           modes are available now. Note that very few authenticated
           encryption algorithms are suitable for disk encryption. You also
           cannot use CRC32 or 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. 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 a proper atomic update, there is a locking mechanism. For
           an image in a file, the code uses the 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>.
    


## CRYPTSETUP



           Part of cryptsetup project
           <https://gitlab.com/cryptsetup/cryptsetup/>. This page is part of
           the _Cryptsetup_ ((open-source disk encryption)) project.
           Information about the project can be found at 
           ⟨https://gitlab.com/cryptsetup/cryptsetup⟩. If you have a bug
           report for this manual page, send it to dm-crypt@saout.de. This
           page was obtained from the project's upstream Git repository
           ⟨https://gitlab.com/cryptsetup/cryptsetup.git⟩ on 2025-08-11. (At
           that time, the date of the most recent commit that was found in
           the repository was 2025-08-01.) If you discover any rendering
           problems in this HTML version of the page, or you believe there is
           a better or more up-to-date source for the page, or you have
           corrections or improvements to the information in this COLOPHON
           (which is _not_ part of the original manual page), send a mail to
           man-pages@man7.org
    
    cryptsetup 2.8.1-git            2025-08-09                  _CRYPTSETUP_(8)
    


* * *