CRYPTSETUP-BENCHMARK(8)	     Maintenance Commands      CRYPTSETUP-BENCHMARK(8)

NAME
       cryptsetup-benchmark - benchmarks ciphers and KDF

SYNOPSIS
       cryptsetup benchmark [<options>]

DESCRIPTION
       Benchmarks, ciphers and KDF (key derivation function).  Without
       parameters, it tries to measure a few common configurations.

       To benchmark other ciphers or modes, specify --cipher and --key-size
       options.

       To benchmark PBKDF you need to specify --pbkdf or --hash with optional
       cost parameters --iter-time, --pbkdf-memory or --pbkdf-parallel.

       This benchmark uses memory only and is only informative.	 You cannot
       directly predict real storage encryption speed from it.

       For testing block ciphers, this benchmark 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).

       <options> can be [--cipher, --key-size, --hash, --pbkdf, --iter-time,
       --pbkdf-memory, --pbkdf-parallel].

OPTIONS
       --batch-mode, -q
	   Suppresses all confirmation questions.  Use with care!

	   If the --verify-passphrase option is not specified, this option
	   also switches off the passphrase verification.

       --cipher, -c <cipher-spec>
	   Set the cipher specification string.

       --debug or --debug-json
	   Run in debug mode with full diagnostic logs.	 Debug output lines
	   are always prefixed by #.

	   If --debug-json is used, additional LUKS2 JSON data structures are
	   printed.

       --hash, -h <hash-spec>
	   The specified hash is used for PBKDF2 and the AF splitter.

       --help, -?
	   Show help text and default parameters.

       --iter-time, -i <number of milliseconds>
	   The number of milliseconds to spend with PBKDF passphrase
	   processing.	Specifying 0 as a parameter selects the compiled-in
	   default.

       --key-size, -s bits
	   Sets key size in bits.  The argument has to be a multiple of 8.
	   The possible key sizes are limited by the cipher and mode used.

	   See /proc/crypto for more information.  Note that the key size in
	   /proc/crypto is stated in bytes.

	   This option can be used for open --type plain or luksFormat.	 All
	   other LUKS actions will use the key size specified in the LUKS
	   header.  Use cryptsetup --help to show the compiled-in defaults.

       --pbkdf <PBKDF spec>
	   Set Password-Based Key Derivation Function (PBKDF) algorithm for
	   LUKS keyslot.  The PBKDF can be: pbkdf2 (for PBKDF2 according to
	   RFC2898), argon2i for Argon2i or argon2id for Argon2id (see Argon2
	   <https://www.cryptolux.org/index.php/Argon2> for more info).

	   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 the cryptsetup --help output.

	   A PBKDF is used for increasing the dictionary and brute-force
	   attack cost for keyslot passwords.  The parameters can be time,
	   memory and parallel cost.

	   For PBKDF2, only the 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 a particular LUKS2 keyslot
	   with the cryptsetup-luksDump(8) command.

	   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 or cause out-of-memory conditions with unconditional process
	   termination.	 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 the maximum is 4294967295 (maximum for 32-bit
	   unsigned integer).  Memory and parallel costs are not supported for
	   PBKDF2.  For Argon2i and Argon2id, the minimum iteration count (CPU
	   cost) is 4, and the maximum is 4294967295 (maximum for a 32-bit
	   unsigned integer).  Minimum memory cost is 32 KiB and maximum is 4
	   GiB.	 If the memory cost parameter is benchmarked (not specified by
	   a parameter), it is always in the range from 64 MiB to 1 GiB.
	   Memory cost above 1GiB (up to the 4GiB maximum) can be setup only
	   by the --pbkdf-memory parameter.  The parallel cost minimum is 1
	   and maximum 4 (if enough CPU cores are available, otherwise it is
	   decreased by the available CPU cores).

	   WARNING: Increasing PBKDF computational costs above the mentioned
	   limits provides negligible additional security improvement.	While
	   elevated costs significantly increase brute-force overhead, they
	   offer negligible protection against dictionary attacks.  The
	   marginal cost increase for processing an entire dictionary remains
	   fundamentally insufficient.

	   The hardcoded PBKDF limits represent engineered trade-offs between
	   cryptographic security and operational usability.  LUKS maintains
	   portability and must be used within a reasonable time on
	   resource-constrained systems.

	   Cryptsetup deliberately restricts maximum memory cost (4 GiB) and
	   parallel cost (4) parameters due to architectural limitations (like
	   embedded and legacy systems).

	   PBKDF memory cost mandates actual physical RAM allocation with
	   intensive write operations that must remain in physical RAM.	 Any
	   swap usage results in unacceptable performance degradation.	Memory
	   management often overcommits allocations beyond available physical
	   memory, expecting most allocated memory to remain unused.  In such
	   situations, as PBKDF always uses all allocated memory, it
	   frequently causes out-of-memory failures that abort cryptsetup
	   operations.

       --pbkdf-memory number
	   Set the memory cost for PBKDF (for Argon2i/id, the number
	   represents kilobytes).  Note that it is the maximal value; PBKDF
	   benchmark or available physical memory can decrease it.  This
	   option is not available for PBKDF2.

       --pbkdf-parallel number
	   Set the parallel cost for PBKDF (number of threads, up to 4).  Note
	   that it is the maximal value; it is decreased automatically if the
	   CPU online count is lower.  This option is not available for
	   PBKDF2.

       --usage
	   Show short option help.

       --version, -V
	   Show the program version.

REPORTING BUGS
       Report bugs at cryptsetup mailing list <cryptsetup@lists.linux.dev> or
       in Issues project section
       <https://gitlab.com/cryptsetup/cryptsetup/-/issues/new>.

       Please attach the output of the failed command with --debug option
       added.

SEE ALSO
       Cryptsetup FAQ
       <https://gitlab.com/cryptsetup/cryptsetup/wikis/FrequentlyAskedQuestions>

       cryptsetup(8), integritysetup(8) and veritysetup(8)

CRYPTSETUP
       Part of cryptsetup project <https://gitlab.com/cryptsetup/cryptsetup/>.

cryptsetup 2.8.1		  2025-08-13	       CRYPTSETUP-BENCHMARK(8)