table of contents
CRYPTSETUP-LUKSCONVERTKEY(8) | Maintenance Commands | CRYPTSETUP-LUKSCONVERTKEY(8) |
NAME¶
cryptsetup-luksConvertKey - converts an existing LUKS2 keyslot to new PBKDF parameters
SYNOPSIS¶
cryptsetup luksConvertKey [<options>] <device>
DESCRIPTION¶
Converts an existing LUKS2 keyslot to new PBKDF parameters. The passphrase for keyslot to be converted must be supplied interactively or via --key-file. If no --pbkdf parameters are specified LUKS2 default PBKDF values will apply.
If a keyslot is specified (via --key-slot), the passphrase for that keyslot must be given. If no keyslot is specified and there is still a free keyslot, then the new parameters will be put into a free keyslot before the keyslot containing the old parameters is purged. If there is no free keyslot, then the keyslot with the old parameters is overwritten directly.
WARNING: If a keyslot is overwritten, a media failure during this operation can cause the overwrite to fail after the old parameters have been wiped and make the LUKS container inaccessible.
<options> can be [--key-file, --keyfile-offset, --keyfile-size, --key-slot, --hash, --header, --disable-locks, --iter-time, --pbkdf, --pbkdf-force-iterations, --pbkdf-memory, --pbkdf-parallel, --keyslot-cipher, --keyslot-key-size, --timeout, --verify-passphrase].
OPTIONS¶
--hash, -h <hash-spec>
--verify-passphrase, -y
--key-file, -d name
If the name given is "-", then the passphrase will be read from stdin. In this case, reading will not stop at newline characters.
See section NOTES ON PASSPHRASE PROCESSING in cryptsetup(8) for more information.
--keyfile-offset value
--keyfile-size, -l value
This option is useful to cut trailing newlines, for example. If --keyfile-offset is also given, the size count starts after the offset.
--new-keyfile-offset value
--new-keyfile-size value
--key-slot, -S <0-N>
The maximum number of key slots depends on the LUKS version. LUKS1 can have up to 8 key slots. LUKS2 can have up to 32 key slots based on key slot area size and key size, but a valid key slot ID can always be between 0 and 31 for LUKS2.
--pbkdf <PBKDF spec>
For LUKS1, only PBKDF2 is accepted (no need to use this option). The default PBKDF for LUKS2 is set during compilation time and is available in cryptsetup --help output.
A PBKDF is used for increasing dictionary and brute-force attack cost for keyslot passwords. The parameters can be time, memory and parallel cost.
For PBKDF2, only time cost (number of iterations) applies. For Argon2i/id, there is also memory cost (memory required during the process of key derivation) and parallel cost (number of threads that run in parallel during the key derivation.
Note that increasing memory cost also increases time, so the final parameter values are measured by a benchmark. The benchmark tries to find iteration time (--iter-time) with required memory cost --pbkdf-memory. If it is not possible, the memory cost is decreased as well. The parallel cost --pbkdf-parallel is constant and is checked against available CPU cores.
You can see all PBKDF parameters for particular LUKS2 keyslot with cryptsetup-luksDump(8) command.
NOTE: If you do not want to use benchmark and want to specify all parameters directly, use --pbkdf-force-iterations with --pbkdf-memory and --pbkdf-parallel. This will override the values without benchmarking. Note it can cause extremely long unlocking time. Use only in specific cases, for example, if you know that the formatted device will be used on some small embedded system.
MINIMAL AND MAXIMAL PBKDF COSTS: For PBKDF2, the minimum iteration count is 1000 and maximum is 4294967295 (maximum for 32bit unsigned integer). Memory and parallel costs are unused for PBKDF2. For Argon2i and Argon2id, minimum iteration count (CPU cost) is 4 and maximum is 4294967295 (maximum for 32bit unsigned integer). Minimum memory cost is 32 KiB and maximum is 4 GiB. (Limited by addressable memory on some CPU platforms.) If the memory cost parameter is benchmarked (not specified by a parameter) it is always in range from 64 MiB to 1 GiB. The parallel cost minimum is 1 and maximum 4 (if enough CPUs cores are available, otherwise it is decreased).
--iter-time, -i <number of milliseconds>
--pbkdf-memory <number>
--pbkdf-parallel <number>
--pbkdf-force-iterations <num>
--timeout, -t <number of seconds>
This option is useful when the system should not stall if the user does not input a passphrase, e.g. during boot. The default is a value of 0 seconds, which means to wait forever.
--header <device or file storing the LUKS header>
For commands that change the LUKS header (e.g. luksAddKey), specify the device or file with the LUKS header directly as the LUKS device.
--force-password
This option is ignored if cryptsetup is built without password quality checking support.
For more info about password quality check, see the manual page for pwquality.conf(5) and passwdqc.conf(5).
--disable-locks
WARNING: Do not use this option unless you run cryptsetup in a restricted environment where locking is impossible to perform (where /run directory cannot be used).
--keyslot-cipher <cipher-spec>
--keyslot-key-size <bits>
--batch-mode, -q
If the --verify-passphrase option is not specified, this option also switches off the passphrase verification.
--debug or --debug-json
If --debug-json is used, additional LUKS2 JSON data structures are printed.
--version, -V
--usage
--help, -?
Report bugs at cryptsetup mailing list <cryptsetup@lists.linux.dev> or in Issues project section <https://gitlab.com/cryptsetup/cryptsetup/-/issues/new>.
Please attach output of the failed command with --debug option added.
SEE ALSO¶
Cryptsetup FAQ <https://gitlab.com/cryptsetup/cryptsetup/wikis/FrequentlyAskedQuestions>
CRYPTSETUP¶
Part of cryptsetup project <https://gitlab.com/cryptsetup/cryptsetup/>.
2023-06-30 | cryptsetup 2.6.0 |