crypto/Kconfig

# SPDX-License-Identifier: GPL-2.0
#
# Generic algorithms support
#
config XOR_BLOCKS
	tristate

#
# async_tx api: hardware offloaded memory transfer/transform support
#
source "crypto/async_tx/Kconfig"

#
# Cryptographic API Configuration
#
menuconfig CRYPTO
	tristate "Cryptographic API"
	select CRYPTO_LIB_UTILS
	help
	  This option provides the core Cryptographic API.

if CRYPTO

menu "Crypto core or helper"

config CRYPTO_FIPS
	bool "FIPS 200 compliance"
	depends on (CRYPTO_ANSI_CPRNG || CRYPTO_DRBG) && !CRYPTO_MANAGER_DISABLE_TESTS
	depends on (MODULE_SIG || !MODULES)
	help
	  This option enables the fips boot option which is
	  required if you want the system to operate in a FIPS 200
	  certification.  You should say no unless you know what
	  this is.

config CRYPTO_FIPS_NAME
	string "FIPS Module Name"
	default "Linux Kernel Cryptographic API"
	depends on CRYPTO_FIPS
	help
	  This option sets the FIPS Module name reported by the Crypto API via
	  the /proc/sys/crypto/fips_name file.

config CRYPTO_FIPS_CUSTOM_VERSION
	bool "Use Custom FIPS Module Version"
	depends on CRYPTO_FIPS
	default n

config CRYPTO_FIPS_VERSION
	string "FIPS Module Version"
	default "(none)"
	depends on CRYPTO_FIPS_CUSTOM_VERSION
	help
	  This option provides the ability to override the FIPS Module Version.
	  By default the KERNELRELEASE value is used.

config CRYPTO_ALGAPI
	tristate
	select CRYPTO_ALGAPI2
	help
	  This option provides the API for cryptographic algorithms.

config CRYPTO_ALGAPI2
	tristate

config CRYPTO_AEAD
	tristate
	select CRYPTO_AEAD2
	select CRYPTO_ALGAPI

config CRYPTO_AEAD2
	tristate
	select CRYPTO_ALGAPI2

config CRYPTO_SIG
	tristate
	select CRYPTO_SIG2
	select CRYPTO_ALGAPI

config CRYPTO_SIG2
	tristate
	select CRYPTO_ALGAPI2

config CRYPTO_SKCIPHER
	tristate
	select CRYPTO_SKCIPHER2
	select CRYPTO_ALGAPI
	select CRYPTO_ECB

config CRYPTO_SKCIPHER2
	tristate
	select CRYPTO_ALGAPI2

config CRYPTO_HASH
	tristate
	select CRYPTO_HASH2
	select CRYPTO_ALGAPI

config CRYPTO_HASH2
	tristate
	select CRYPTO_ALGAPI2

config CRYPTO_RNG
	tristate
	select CRYPTO_RNG2
	select CRYPTO_ALGAPI

config CRYPTO_RNG2
	tristate
	select CRYPTO_ALGAPI2

config CRYPTO_RNG_DEFAULT
	tristate
	select CRYPTO_DRBG_MENU

config CRYPTO_AKCIPHER2
	tristate
	select CRYPTO_ALGAPI2

config CRYPTO_AKCIPHER
	tristate
	select CRYPTO_AKCIPHER2
	select CRYPTO_ALGAPI

config CRYPTO_KPP2
	tristate
	select CRYPTO_ALGAPI2

config CRYPTO_KPP
	tristate
	select CRYPTO_ALGAPI
	select CRYPTO_KPP2

config CRYPTO_ACOMP2
	tristate
	select CRYPTO_ALGAPI2
	select SGL_ALLOC

config CRYPTO_ACOMP
	tristate
	select CRYPTO_ALGAPI
	select CRYPTO_ACOMP2

config CRYPTO_MANAGER
	tristate "Cryptographic algorithm manager"
	select CRYPTO_MANAGER2
	help
	  Create default cryptographic template instantiations such as
	  cbc(aes).

config CRYPTO_MANAGER2
	def_tristate CRYPTO_MANAGER || (CRYPTO_MANAGER!=n && CRYPTO_ALGAPI=y)
	select CRYPTO_ACOMP2
	select CRYPTO_AEAD2
	select CRYPTO_AKCIPHER2
	select CRYPTO_SIG2
	select CRYPTO_HASH2
	select CRYPTO_KPP2
	select CRYPTO_RNG2
	select CRYPTO_SKCIPHER2

config CRYPTO_USER
	tristate "Userspace cryptographic algorithm configuration"
	depends on NET
	select CRYPTO_MANAGER
	help
	  Userspace configuration for cryptographic instantiations such as
	  cbc(aes).

config CRYPTO_MANAGER_DISABLE_TESTS
	bool "Disable run-time self tests"
	default y
	help
	  Disable run-time self tests that normally take place at
	  algorithm registration.

config CRYPTO_MANAGER_EXTRA_TESTS
	bool "Enable extra run-time crypto self tests"
	depends on DEBUG_KERNEL && !CRYPTO_MANAGER_DISABLE_TESTS && CRYPTO_MANAGER
	help
	  Enable extra run-time self tests of registered crypto algorithms,
	  including randomized fuzz tests.

	  This is intended for developer use only, as these tests take much
	  longer to run than the normal self tests.

config CRYPTO_NULL
	tristate "Null algorithms"
	select CRYPTO_NULL2
	help
	  These are 'Null' algorithms, used by IPsec, which do nothing.

config CRYPTO_NULL2
	tristate
	select CRYPTO_ALGAPI2
	select CRYPTO_SKCIPHER2
	select CRYPTO_HASH2

config CRYPTO_PCRYPT
	tristate "Parallel crypto engine"
	depends on SMP
	select PADATA
	select CRYPTO_MANAGER
	select CRYPTO_AEAD
	help
	  This converts an arbitrary crypto algorithm into a parallel
	  algorithm that executes in kernel threads.

config CRYPTO_CRYPTD
	tristate "Software async crypto daemon"
	select CRYPTO_SKCIPHER
	select CRYPTO_HASH
	select CRYPTO_MANAGER
	help
	  This is a generic software asynchronous crypto daemon that
	  converts an arbitrary synchronous software crypto algorithm
	  into an asynchronous algorithm that executes in a kernel thread.

config CRYPTO_AUTHENC
	tristate "Authenc support"
	select CRYPTO_AEAD
	select CRYPTO_SKCIPHER
	select CRYPTO_MANAGER
	select CRYPTO_HASH
	select CRYPTO_NULL
	help
	  Authenc: Combined mode wrapper for IPsec.

	  This is required for IPSec ESP (XFRM_ESP).

config CRYPTO_TEST
	tristate "Testing module"
	depends on m || EXPERT
	select CRYPTO_MANAGER
	help
	  Quick & dirty crypto test module.

config CRYPTO_SIMD
	tristate
	select CRYPTO_CRYPTD

config CRYPTO_ENGINE
	tristate

endmenu

menu "Public-key cryptography"

config CRYPTO_RSA
	tristate "RSA (Rivest-Shamir-Adleman)"
	select CRYPTO_AKCIPHER
	select CRYPTO_MANAGER
	select MPILIB
	select ASN1
	help
	  RSA (Rivest-Shamir-Adleman) public key algorithm (RFC8017)

config CRYPTO_DH
	tristate "DH (Diffie-Hellman)"
	select CRYPTO_KPP
	select MPILIB
	help
	  DH (Diffie-Hellman) key exchange algorithm

config CRYPTO_DH_RFC7919_GROUPS
	bool "RFC 7919 FFDHE groups"
	depends on CRYPTO_DH
	select CRYPTO_RNG_DEFAULT
	help
	  FFDHE (Finite-Field-based Diffie-Hellman Ephemeral) groups
	  defined in RFC7919.

	  Support these finite-field groups in DH key exchanges:
	  - ffdhe2048, ffdhe3072, ffdhe4096, ffdhe6144, ffdhe8192

	  If unsure, say N.

config CRYPTO_ECC
	tristate
	select CRYPTO_RNG_DEFAULT

config CRYPTO_ECDH
	tristate "ECDH (Elliptic Curve Diffie-Hellman)"
	select CRYPTO_ECC
	select CRYPTO_KPP
	help
	  ECDH (Elliptic Curve Diffie-Hellman) key exchange algorithm
	  using curves P-192, P-256, and P-384 (FIPS 186)

config CRYPTO_ECDSA
	tristate "ECDSA (Elliptic Curve Digital Signature Algorithm)"
	select CRYPTO_ECC
	select CRYPTO_AKCIPHER
	select ASN1
	help
	  ECDSA (Elliptic Curve Digital Signature Algorithm) (FIPS 186,
	  ISO/IEC 14888-3)
	  using curves P-192, P-256, and P-384

	  Only signature verification is implemented.

config CRYPTO_ECRDSA
	tristate "EC-RDSA (Elliptic Curve Russian Digital Signature Algorithm)"
	select CRYPTO_ECC
	select CRYPTO_AKCIPHER
	select CRYPTO_STREEBOG
	select OID_REGISTRY
	select ASN1
	help
	  Elliptic Curve Russian Digital Signature Algorithm (GOST R 34.10-2012,
	  RFC 7091, ISO/IEC 14888-3)

	  One of the Russian cryptographic standard algorithms (called GOST
	  algorithms). Only signature verification is implemented.

config CRYPTO_SM2
	tristate "SM2 (ShangMi 2)"
	select CRYPTO_SM3
	select CRYPTO_AKCIPHER
	select CRYPTO_MANAGER
	select MPILIB
	select ASN1
	help
	  SM2 (ShangMi 2) public key algorithm

	  Published by State Encryption Management Bureau, China,
	  as specified by OSCCA GM/T 0003.1-2012 -- 0003.5-2012.

	  References:
	  https://datatracker.ietf.org/doc/draft-shen-sm2-ecdsa/
	  http://www.oscca.gov.cn/sca/xxgk/2010-12/17/content_1002386.shtml
	  http://www.gmbz.org.cn/main/bzlb.html

config CRYPTO_CURVE25519
	tristate "Curve25519"
	select CRYPTO_KPP
	select CRYPTO_LIB_CURVE25519_GENERIC
	help
	  Curve25519 elliptic curve (RFC7748)

endmenu

menu "Block ciphers"

config CRYPTO_AES
	tristate "AES (Advanced Encryption Standard)"
	select CRYPTO_ALGAPI
	select CRYPTO_LIB_AES
	help
	  AES cipher algorithms (Rijndael)(FIPS-197, ISO/IEC 18033-3)

	  Rijndael appears to be consistently a very good performer in
	  both hardware and software across a wide range of computing
	  environments regardless of its use in feedback or non-feedback
	  modes. Its key setup time is excellent, and its key agility is
	  good. Rijndael's very low memory requirements make it very well
	  suited for restricted-space environments, in which it also
	  demonstrates excellent performance. Rijndael's operations are
	  among the easiest to defend against power and timing attacks.

	  The AES specifies three key sizes: 128, 192 and 256 bits

config CRYPTO_AES_TI
	tristate "AES (Advanced Encryption Standard) (fixed time)"
	select CRYPTO_ALGAPI
	select CRYPTO_LIB_AES
	help
	  AES cipher algorithms (Rijndael)(FIPS-197, ISO/IEC 18033-3)

	  This is a generic implementation of AES that attempts to eliminate
	  data dependent latencies as much as possible without affecting
	  performance too much. It is intended for use by the generic CCM
	  and GCM drivers, and other CTR or CMAC/XCBC based modes that rely
	  solely on encryption (although decryption is supported as well, but
	  with a more dramatic performance hit)

	  Instead of using 16 lookup tables of 1 KB each, (8 for encryption and
	  8 for decryption), this implementation only uses just two S-boxes of
	  256 bytes each, and attempts to eliminate data dependent latencies by
	  prefetching the entire table into the cache at the start of each
	  block. Interrupts are also disabled to avoid races where cachelines
	  are evicted when the CPU is interrupted to do something else.

config CRYPTO_ANUBIS
	tristate "Anubis"
	depends on CRYPTO_USER_API_ENABLE_OBSOLETE
	select CRYPTO_ALGAPI
	help
	  Anubis cipher algorithm

	  Anubis is a variable key length cipher which can use keys from
	  128 bits to 320 bits in length.  It was evaluated as a entrant
	  in the NESSIE competition.

	  See https://web.archive.org/web/20160606112246/http://www.larc.usp.br/~pbarreto/AnubisPage.html
	  for further information.

config CRYPTO_ARIA
	tristate "ARIA"
	select CRYPTO_ALGAPI
	help
	  ARIA cipher algorithm (RFC5794)

	  ARIA is a standard encryption algorithm of the Republic of Korea.
	  The ARIA specifies three key sizes and rounds.
	  128-bit: 12 rounds.
	  192-bit: 14 rounds.
	  256-bit: 16 rounds.

	  See:
	  https://seed.kisa.or.kr/kisa/algorithm/EgovAriaInfo.do

config CRYPTO_BLOWFISH
	tristate "Blowfish"
	select CRYPTO_ALGAPI
	select CRYPTO_BLOWFISH_COMMON
	help
	  Blowfish cipher algorithm, by Bruce Schneier

	  This is a variable key length cipher which can use keys from 32
	  bits to 448 bits in length.  It's fast, simple and specifically
	  designed for use on "large microprocessors".

	  See https://www.schneier.com/blowfish.html for further information.

config CRYPTO_BLOWFISH_COMMON
	tristate
	help
	  Common parts of the Blowfish cipher algorithm shared by the
	  generic c and the assembler implementations.

config CRYPTO_CAMELLIA
	tristate "Camellia"
	select CRYPTO_ALGAPI
	help
	  Camellia cipher algorithms (ISO/IEC 18033-3)

	  Camellia is a symmetric key block cipher developed jointly
	  at NTT and Mitsubishi Electric Corporation.

	  The Camellia specifies three key sizes: 128, 192 and 256 bits.

	  See https://info.isl.ntt.co.jp/crypt/eng/camellia/ for further information.

config CRYPTO_CAST_COMMON
	tristate
	help
	  Common parts of the CAST cipher algorithms shared by the
	  generic c and the assembler implementations.

config CRYPTO_CAST5
	tristate "CAST5 (CAST-128)"
	select CRYPTO_ALGAPI
	select CRYPTO_CAST_COMMON
	help
	  CAST5 (CAST-128) cipher algorithm (RFC2144, ISO/IEC 18033-3)

config CRYPTO_CAST6
	tristate "CAST6 (CAST-256)"
	select CRYPTO_ALGAPI
	select CRYPTO_CAST_COMMON
	help
	  CAST6 (CAST-256) encryption algorithm (RFC2612)

config CRYPTO_DES
	tristate "DES and Triple DES EDE"
	select CRYPTO_ALGAPI
	select CRYPTO_LIB_DES
	help
	  DES (Data Encryption Standard)(FIPS 46-2, ISO/IEC 18033-3) and
	  Triple DES EDE (Encrypt/Decrypt/Encrypt) (FIPS 46-3, ISO/IEC 18033-3)
	  cipher algorithms

config CRYPTO_FCRYPT
	tristate "FCrypt"
	select CRYPTO_ALGAPI
	select CRYPTO_SKCIPHER
	help
	  FCrypt algorithm used by RxRPC

	  See https://ota.polyonymo.us/fcrypt-paper.txt

config CRYPTO_KHAZAD
	tristate "Khazad"
	depends on CRYPTO_USER_API_ENABLE_OBSOLETE
	select CRYPTO_ALGAPI
	help
	  Khazad cipher algorithm

	  Khazad was a finalist in the initial NESSIE competition.  It is
	  an algorithm optimized for 64-bit processors with good performance
	  on 32-bit processors.  Khazad uses an 128 bit key size.

	  See https://web.archive.org/web/20171011071731/http://www.larc.usp.br/~pbarreto/KhazadPage.html
	  for further information.

config CRYPTO_SEED
	tristate "SEED"
	depends on CRYPTO_USER_API_ENABLE_OBSOLETE
	select CRYPTO_ALGAPI
	help
	  SEED cipher algorithm (RFC4269, ISO/IEC 18033-3)

	  SEED is a 128-bit symmetric key block cipher that has been
	  developed by KISA (Korea Information Security Agency) as a
	  national standard encryption algorithm of the Republic of Korea.
	  It is a 16 round block cipher with the key size of 128 bit.

	  See https://seed.kisa.or.kr/kisa/algorithm/EgovSeedInfo.do
	  for further information.

config CRYPTO_SERPENT
	tristate "Serpent"
	select CRYPTO_ALGAPI
	help
	  Serpent cipher algorithm, by Anderson, Biham & Knudsen

	  Keys are allowed to be from 0 to 256 bits in length, in steps
	  of 8 bits.

	  See https://www.cl.cam.ac.uk/~rja14/serpent.html for further information.

config CRYPTO_SM4
	tristate

config CRYPTO_SM4_GENERIC
	tristate "SM4 (ShangMi 4)"
	select CRYPTO_ALGAPI
	select CRYPTO_SM4
	help
	  SM4 cipher algorithms (OSCCA GB/T 32907-2016,
	  ISO/IEC 18033-3:2010/Amd 1:2021)

	  SM4 (GBT.32907-2016) is a cryptographic standard issued by the
	  Organization of State Commercial Administration of China (OSCCA)
	  as an authorized cryptographic algorithms for the use within China.

	  SMS4 was originally created for use in protecting wireless
	  networks, and is mandated in the Chinese National Standard for
	  Wireless LAN WAPI (Wired Authentication and Privacy Infrastructure)
	  (GB.15629.11-2003).

	  The latest SM4 standard (GBT.32907-2016) was proposed by OSCCA and
	  standardized through TC 260 of the Standardization Administration
	  of the People's Republic of China (SAC).

	  The input, output, and key of SMS4 are each 128 bits.

	  See https://eprint.iacr.org/2008/329.pdf for further information.

	  If unsure, say N.

config CRYPTO_TEA
	tristate "TEA, XTEA and XETA"
	depends on CRYPTO_USER_API_ENABLE_OBSOLETE
	select CRYPTO_ALGAPI
	help
	  TEA (Tiny Encryption Algorithm) cipher algorithms

	  Tiny Encryption Algorithm is a simple cipher that uses
	  many rounds for security.  It is very fast and uses
	  little memory.

	  Xtendend Tiny Encryption Algorithm is a modification to
	  the TEA algorithm to address a potential key weakness
	  in the TEA algorithm.

	  Xtendend Encryption Tiny Algorithm is a mis-implementation
	  of the XTEA algorithm for compatibility purposes.

config CRYPTO_TWOFISH
	tristate "Twofish"
	select CRYPTO_ALGAPI
	select CRYPTO_TWOFISH_COMMON
	help
	  Twofish cipher algorithm

	  Twofish was submitted as an AES (Advanced Encryption Standard)
	  candidate cipher by researchers at CounterPane Systems.  It is a
	  16 round block cipher supporting key sizes of 128, 192, and 256
	  bits.

	  See https://www.schneier.com/twofish.html for further information.

config CRYPTO_TWOFISH_COMMON
	tristate
	help
	  Common parts of the Twofish cipher algorithm shared by the
	  generic c and the assembler implementations.

endmenu

menu "Length-preserving ciphers and modes"

config CRYPTO_ADIANTUM
	tristate "Adiantum"
	select CRYPTO_CHACHA20
	select CRYPTO_LIB_POLY1305_GENERIC
	select CRYPTO_NHPOLY1305
	select CRYPTO_MANAGER
	help
	  Adiantum tweakable, length-preserving encryption mode

	  Designed for fast and secure disk encryption, especially on
	  CPUs without dedicated crypto instructions.  It encrypts
	  each sector using the XChaCha12 stream cipher, two passes of
	  an ε-almost-∆-universal hash function, and an invocation of
	  the AES-256 block cipher on a single 16-byte block.  On CPUs
	  without AES instructions, Adiantum is much faster than
	  AES-XTS.

	  Adiantum's security is provably reducible to that of its
	  underlying stream and block ciphers, subject to a security
	  bound.  Unlike XTS, Adiantum is a true wide-block encryption
	  mode, so it actually provides an even stronger notion of
	  security than XTS, subject to the security bound.

	  If unsure, say N.

config CRYPTO_ARC4
	tristate "ARC4 (Alleged Rivest Cipher 4)"
	depends on CRYPTO_USER_API_ENABLE_OBSOLETE
	select CRYPTO_SKCIPHER
	select CRYPTO_LIB_ARC4
	help
	  ARC4 cipher algorithm

	  ARC4 is a stream cipher using keys ranging from 8 bits to 2048
	  bits in length.  This algorithm is required for driver-based
	  WEP, but it should not be for other purposes because of the
	  weakness of the algorithm.

config CRYPTO_CHACHA20
	tristate "ChaCha"
	select CRYPTO_LIB_CHACHA_GENERIC
	select CRYPTO_SKCIPHER
	help
	  The ChaCha20, XChaCha20, and XChaCha12 stream cipher algorithms

	  ChaCha20 is a 256-bit high-speed stream cipher designed by Daniel J.
	  Bernstein and further specified in RFC7539 for use in IETF protocols.
	  This is the portable C implementation of ChaCha20.  See
	  https://cr.yp.to/chacha/chacha-20080128.pdf for further information.

	  XChaCha20 is the application of the XSalsa20 construction to ChaCha20
	  rather than to Salsa20.  XChaCha20 extends ChaCha20's nonce length
	  from 64 bits (or 96 bits using the RFC7539 convention) to 192 bits,
	  while provably retaining ChaCha20's security.  See
	  https://cr.yp.to/snuffle/xsalsa-20081128.pdf for further information.

	  XChaCha12 is XChaCha20 reduced to 12 rounds, with correspondingly
	  reduced security margin but increased performance.  It can be needed
	  in some performance-sensitive scenarios.

config CRYPTO_CBC
	tristate "CBC (Cipher Block Chaining)"
	select CRYPTO_SKCIPHER
	select CRYPTO_MANAGER
	help
	  CBC (Cipher Block Chaining) mode (NIST SP800-38A)

	  This block cipher mode is required for IPSec ESP (XFRM_ESP).

config CRYPTO_CTR
	tristate "CTR (Counter)"
	select CRYPTO_SKCIPHER
	select CRYPTO_MANAGER
	help
	  CTR (Counter) mode (NIST SP800-38A)

config CRYPTO_CTS
	tristate "CTS (Cipher Text Stealing)"
	select CRYPTO_SKCIPHER
	select CRYPTO_MANAGER
	help
	  CBC-CS3 variant of CTS (Cipher Text Stealing) (NIST
	  Addendum to SP800-38A (October 2010))

	  This mode is required for Kerberos gss mechanism support
	  for AES encryption.

config CRYPTO_ECB
	tristate "ECB (Electronic Codebook)"
	select CRYPTO_SKCIPHER2
	select CRYPTO_MANAGER
	help
	  ECB (Electronic Codebook) mode (NIST SP800-38A)

config CRYPTO_HCTR2
	tristate "HCTR2"
	select CRYPTO_XCTR
	select CRYPTO_POLYVAL
	select CRYPTO_MANAGER
	help
	  HCTR2 length-preserving encryption mode

	  A mode for storage encryption that is efficient on processors with
	  instructions to accelerate AES and carryless multiplication, e.g.
	  x86 processors with AES-NI and CLMUL, and ARM processors with the
	  ARMv8 crypto extensions.

	  See https://eprint.iacr.org/2021/1441

config CRYPTO_KEYWRAP
	tristate "KW (AES Key Wrap)"
	select CRYPTO_SKCIPHER
	select CRYPTO_MANAGER
	help
	  KW (AES Key Wrap) authenticated encryption mode (NIST SP800-38F
	  and RFC3394) without padding.

config CRYPTO_LRW
	tristate "LRW (Liskov Rivest Wagner)"
	select CRYPTO_LIB_GF128MUL
	select CRYPTO_SKCIPHER
	select CRYPTO_MANAGER
	select CRYPTO_ECB
	help
	  LRW (Liskov Rivest Wagner) mode

	  A tweakable, non malleable, non movable
	  narrow block cipher mode for dm-crypt.  Use it with cipher
	  specification string aes-lrw-benbi, the key must be 256, 320 or 384.
	  The first 128, 192 or 256 bits in the key are used for AES and the
	  rest is used to tie each cipher block to its logical position.

	  See https://people.csail.mit.edu/rivest/pubs/LRW02.pdf

config CRYPTO_PCBC
	tristate "PCBC (Propagating Cipher Block Chaining)"
	select CRYPTO_SKCIPHER
	select CRYPTO_MANAGER
	help
	  PCBC (Propagating Cipher Block Chaining) mode

	  This block cipher mode is required for RxRPC.

config CRYPTO_XCTR
	tristate
	select CRYPTO_SKCIPHER
	select CRYPTO_MANAGER
	help
	  XCTR (XOR Counter) mode for HCTR2

	  This blockcipher mode is a variant of CTR mode using XORs and little-endian
	  addition rather than big-endian arithmetic.

	  XCTR mode is used to implement HCTR2.

config CRYPTO_XTS
	tristate "XTS (XOR Encrypt XOR with ciphertext stealing)"
	select CRYPTO_SKCIPHER
	select CRYPTO_MANAGER
	select CRYPTO_ECB
	help
	  XTS (XOR Encrypt XOR with ciphertext stealing) mode (NIST SP800-38E
	  and IEEE 1619)

	  Use with aes-xts-plain, key size 256, 384 or 512 bits. This
	  implementation currently can't handle a sectorsize which is not a
	  multiple of 16 bytes.

config CRYPTO_NHPOLY1305
	tristate
	select CRYPTO_HASH
	select CRYPTO_LIB_POLY1305_GENERIC

endmenu

menu "AEAD (authenticated encryption with associated data) ciphers"

config CRYPTO_AEGIS128
	tristate "AEGIS-128"
	select CRYPTO_AEAD
	select CRYPTO_AES  # for AES S-box tables
	help
	  AEGIS-128 AEAD algorithm

config CRYPTO_AEGIS128_SIMD
	bool "AEGIS-128 (arm NEON, arm64 NEON)"
	depends on CRYPTO_AEGIS128 && ((ARM || ARM64) && KERNEL_MODE_NEON)
	default y
	help
	  AEGIS-128 AEAD algorithm

	  Architecture: arm or arm64 using:
	  - NEON (Advanced SIMD) extension

config CRYPTO_CHACHA20POLY1305
	tristate "ChaCha20-Poly1305"
	select CRYPTO_CHACHA20
	select CRYPTO_POLY1305
	select CRYPTO_AEAD
	select CRYPTO_MANAGER
	help
	  ChaCha20 stream cipher and Poly1305 authenticator combined
	  mode (RFC8439)

config CRYPTO_CCM
	tristate "CCM (Counter with Cipher Block Chaining-MAC)"
	select CRYPTO_CTR
	select CRYPTO_HASH
	select CRYPTO_AEAD
	select CRYPTO_MANAGER
	help
	  CCM (Counter with Cipher Block Chaining-Message Authentication Code)
	  authenticated encryption mode (NIST SP800-38C)

config CRYPTO_GCM
	tristate "GCM (Galois/Counter Mode) and GMAC (GCM MAC)"
	select CRYPTO_CTR
	select CRYPTO_AEAD
	select CRYPTO_GHASH
	select CRYPTO_NULL
	select CRYPTO_MANAGER
	help
	  GCM (Galois/Counter Mode) authenticated encryption mode and GMAC
	  (GCM Message Authentication Code) (NIST SP800-38D)

	  This is required for IPSec ESP (XFRM_ESP).

config CRYPTO_GENIV
	tristate
	select CRYPTO_AEAD
	select CRYPTO_NULL
	select CRYPTO_MANAGER
	select CRYPTO_RNG_DEFAULT

config CRYPTO_SEQIV
	tristate "Sequence Number IV Generator"
	select CRYPTO_GENIV
	help
	  Sequence Number IV generator

	  This IV generator generates an IV based on a sequence number by
	  xoring it with a salt.  This algorithm is mainly useful for CTR.

	  This is required for IPsec ESP (XFRM_ESP).

config CRYPTO_ECHAINIV
	tristate "Encrypted Chain IV Generator"
	select CRYPTO_GENIV
	help
	  Encrypted Chain IV generator

	  This IV generator generates an IV based on the encryption of
	  a sequence number xored with a salt.  This is the default
	  algorithm for CBC.

config CRYPTO_ESSIV
	tristate "Encrypted Salt-Sector IV Generator"
	select CRYPTO_AUTHENC
	help
	  Encrypted Salt-Sector IV generator

	  This IV generator is used in some cases by fscrypt and/or
	  dm-crypt. It uses the hash of the block encryption key as the
	  symmetric key for a block encryption pass applied to the input
	  IV, making low entropy IV sources more suitable for block
	  encryption.

	  This driver implements a crypto API template that can be
	  instantiated either as an skcipher or as an AEAD (depending on the
	  type of the first template argument), and which defers encryption
	  and decryption requests to the encapsulated cipher after applying
	  ESSIV to the input IV. Note that in the AEAD case, it is assumed
	  that the keys are presented in the same format used by the authenc
	  template, and that the IV appears at the end of the authenticated
	  associated data (AAD) region (which is how dm-crypt uses it.)

	  Note that the use of ESSIV is not recommended for new deployments,
	  and so this only needs to be enabled when interoperability with
	  existing encrypted volumes of filesystems is required, or when
	  building for a particular system that requires it (e.g., when
	  the SoC in question has accelerated CBC but not XTS, making CBC
	  combined with ESSIV the only feasible mode for h/w accelerated
	  block encryption)

endmenu

menu "Hashes, digests, and MACs"

config CRYPTO_BLAKE2B
	tristate "BLAKE2b"
	select CRYPTO_HASH
	help
	  BLAKE2b cryptographic hash function (RFC 7693)

	  BLAKE2b is optimized for 64-bit platforms and can produce digests
	  of any size between 1 and 64 bytes. The keyed hash is also implemented.

	  This module provides the following algorithms:
	  - blake2b-160
	  - blake2b-256
	  - blake2b-384
	  - blake2b-512

	  Used by the btrfs filesystem.

	  See https://blake2.net for further information.

config CRYPTO_CMAC
	tristate "CMAC (Cipher-based MAC)"
	select CRYPTO_HASH
	select CRYPTO_MANAGER
	help
	  CMAC (Cipher-based Message Authentication Code) authentication
	  mode (NIST SP800-38B and IETF RFC4493)

config CRYPTO_GHASH
	tristate "GHASH"
	select CRYPTO_HASH
	select CRYPTO_LIB_GF128MUL
	help
	  GCM GHASH function (NIST SP800-38D)

config CRYPTO_HMAC
	tristate "HMAC (Keyed-Hash MAC)"
	select CRYPTO_HASH
	select CRYPTO_MANAGER
	help
	  HMAC (Keyed-Hash Message Authentication Code) (FIPS 198 and
	  RFC2104)

	  This is required for IPsec AH (XFRM_AH) and IPsec ESP (XFRM_ESP).

config CRYPTO_MD4
	tristate "MD4"
	select CRYPTO_HASH
	help
	  MD4 message digest algorithm (RFC1320)

config CRYPTO_MD5
	tristate "MD5"
	select CRYPTO_HASH
	help
	  MD5 message digest algorithm (RFC1321)

config CRYPTO_MICHAEL_MIC
	tristate "Michael MIC"
	select CRYPTO_HASH
	help
	  Michael MIC (Message Integrity Code) (IEEE 802.11i)

	  Defined by the IEEE 802.11i TKIP (Temporal Key Integrity Protocol),
	  known as WPA (Wif-Fi Protected Access).

	  This algorithm is required for TKIP, but it should not be used for
	  other purposes because of the weakness of the algorithm.

config CRYPTO_POLYVAL
	tristate
	select CRYPTO_HASH
	select CRYPTO_LIB_GF128MUL
	help
	  POLYVAL hash function for HCTR2

	  This is used in HCTR2.  It is not a general-purpose
	  cryptographic hash function.

config CRYPTO_POLY1305
	tristate "Poly1305"
	select CRYPTO_HASH
	select CRYPTO_LIB_POLY1305_GENERIC
	help
	  Poly1305 authenticator algorithm (RFC7539)

	  Poly1305 is an authenticator algorithm designed by Daniel J. Bernstein.
	  It is used for the ChaCha20-Poly1305 AEAD, specified in RFC7539 for use
	  in IETF protocols. This is the portable C implementation of Poly1305.

config CRYPTO_RMD160
	tristate "RIPEMD-160"
	select CRYPTO_HASH
	help
	  RIPEMD-160 hash function (ISO/IEC 10118-3)

	  RIPEMD-160 is a 160-bit cryptographic hash function. It is intended
	  to be used as a secure replacement for the 128-bit hash functions
	  MD4, MD5 and its predecessor RIPEMD
	  (not to be confused with RIPEMD-128).

	  Its speed is comparable to SHA-1 and there are no known attacks
	  against RIPEMD-160.

	  Developed by Hans Dobbertin, Antoon Bosselaers and Bart Preneel.
	  See https://homes.esat.kuleuven.be/~bosselae/ripemd160.html
	  for further information.

config CRYPTO_SHA1
	tristate "SHA-1"
	select CRYPTO_HASH
	select CRYPTO_LIB_SHA1
	help
	  SHA-1 secure hash algorithm (FIPS 180, ISO/IEC 10118-3)

config CRYPTO_SHA256
	tristate "SHA-224 and SHA-256"
	select CRYPTO_HASH
	select CRYPTO_LIB_SHA256
	help
	  SHA-224 and SHA-256 secure hash algorithms (FIPS 180, ISO/IEC 10118-3)

	  This is required for IPsec AH (XFRM_AH) and IPsec ESP (XFRM_ESP).
	  Used by the btrfs filesystem, Ceph, NFS, and SMB.

config CRYPTO_SHA512
	tristate "SHA-384 and SHA-512"
	select CRYPTO_HASH
	help
	  SHA-384 and SHA-512 secure hash algorithms (FIPS 180, ISO/IEC 10118-3)

config CRYPTO_SHA3
	tristate "SHA-3"
	select CRYPTO_HASH
	help
	  SHA-3 secure hash algorithms (FIPS 202, ISO/IEC 10118-3)

config CRYPTO_SM3
	tristate

config CRYPTO_SM3_GENERIC
	tristate "SM3 (ShangMi 3)"
	select CRYPTO_HASH
	select CRYPTO_SM3
	help
	  SM3 (ShangMi 3) secure hash function (OSCCA GM/T 0004-2012, ISO/IEC 10118-3)

	  This is part of the Chinese Commercial Cryptography suite.

	  References:
	  http://www.oscca.gov.cn/UpFile/20101222141857786.pdf
	  https://datatracker.ietf.org/doc/html/draft-shen-sm3-hash

config CRYPTO_STREEBOG
	tristate "Streebog"
	select CRYPTO_HASH
	help
	  Streebog Hash Function (GOST R 34.11-2012, RFC 6986, ISO/IEC 10118-3)

	  This is one of the Russian cryptographic standard algorithms (called
	  GOST algorithms). This setting enables two hash algorithms with
	  256 and 512 bits output.

	  References:
	  https://tc26.ru/upload/iblock/fed/feddbb4d26b685903faa2ba11aea43f6.pdf
	  https://tools.ietf.org/html/rfc6986

config CRYPTO_VMAC
	tristate "VMAC"
	select CRYPTO_HASH
	select CRYPTO_MANAGER
	help
	  VMAC is a message authentication algorithm designed for
	  very high speed on 64-bit architectures.

	  See https://fastcrypto.org/vmac for further information.

config CRYPTO_WP512
	tristate "Whirlpool"
	select CRYPTO_HASH
	help
	  Whirlpool hash function (ISO/IEC 10118-3)

	  512, 384 and 256-bit hashes.

	  Whirlpool-512 is part of the NESSIE cryptographic primitives.

	  See https://web.archive.org/web/20171129084214/http://www.larc.usp.br/~pbarreto/WhirlpoolPage.html
	  for further information.

config CRYPTO_XCBC
	tristate "XCBC-MAC (Extended Cipher Block Chaining MAC)"
	select CRYPTO_HASH
	select CRYPTO_MANAGER
	help
	  XCBC-MAC (Extended Cipher Block Chaining Message Authentication
	  Code) (RFC3566)

config CRYPTO_XXHASH
	tristate "xxHash"
	select CRYPTO_HASH
	select XXHASH
	help
	  xxHash non-cryptographic hash algorithm

	  Extremely fast, working at speeds close to RAM limits.

	  Used by the btrfs filesystem.

endmenu

menu "CRCs (cyclic redundancy checks)"

config CRYPTO_CRC32C
	tristate "CRC32c"
	select CRYPTO_HASH
	select CRC32
	help
	  CRC32c CRC algorithm with the iSCSI polynomial (RFC 3385 and RFC 3720)

	  A 32-bit CRC (cyclic redundancy check) with a polynomial defined
	  by G. Castagnoli, S. Braeuer and M. Herrman in "Optimization of Cyclic
	  Redundancy-Check Codes with 24 and 32 Parity Bits", IEEE Transactions
	  on Communications, Vol. 41, No. 6, June 1993, selected for use with
	  iSCSI.

	  Used by btrfs, ext4, jbd2, NVMeoF/TCP, and iSCSI.

config CRYPTO_CRC32
	tristate "CRC32"
	select CRYPTO_HASH
	select CRC32
	help
	  CRC32 CRC algorithm (IEEE 802.3)

	  Used by RoCEv2 and f2fs.

config CRYPTO_CRCT10DIF
	tristate "CRCT10DIF"
	select CRYPTO_HASH
	help
	  CRC16 CRC algorithm used for the T10 (SCSI) Data Integrity Field (DIF)

	  CRC algorithm used by the SCSI Block Commands standard.

config CRYPTO_CRC64_ROCKSOFT
	tristate "CRC64 based on Rocksoft Model algorithm"
	depends on CRC64
	select CRYPTO_HASH
	help
	  CRC64 CRC algorithm based on the Rocksoft Model CRC Algorithm

	  Used by the NVMe implementation of T10 DIF (BLK_DEV_INTEGRITY)

	  See https://zlib.net/crc_v3.txt

endmenu

menu "Compression"

config CRYPTO_DEFLATE
	tristate "Deflate"
	select CRYPTO_ALGAPI
	select CRYPTO_ACOMP2
	select ZLIB_INFLATE
	select ZLIB_DEFLATE
	help
	  Deflate compression algorithm (RFC1951)

	  Used by IPSec with the IPCOMP protocol (RFC3173, RFC2394)

config CRYPTO_LZO
	tristate "LZO"
	select CRYPTO_ALGAPI
	select CRYPTO_ACOMP2
	select LZO_COMPRESS
	select LZO_DECOMPRESS
	help
	  LZO compression algorithm

	  See https://www.oberhumer.com/opensource/lzo/ for further information.

config CRYPTO_842
	tristate "842"
	select CRYPTO_ALGAPI
	select CRYPTO_ACOMP2
	select 842_COMPRESS
	select 842_DECOMPRESS
	help
	  842 compression algorithm by IBM

	  See https://github.com/plauth/lib842 for further information.

config CRYPTO_LZ4
	tristate "LZ4"
	select CRYPTO_ALGAPI
	select CRYPTO_ACOMP2
	select LZ4_COMPRESS
	select LZ4_DECOMPRESS
	help
	  LZ4 compression algorithm

	  See https://github.com/lz4/lz4 for further information.

config CRYPTO_LZ4HC
	tristate "LZ4HC"
	select CRYPTO_ALGAPI
	select CRYPTO_ACOMP2
	select LZ4HC_COMPRESS
	select LZ4_DECOMPRESS
	help
	  LZ4 high compression mode algorithm

	  See https://github.com/lz4/lz4 for further information.

config CRYPTO_ZSTD
	tristate "Zstd"
	select CRYPTO_ALGAPI
	select CRYPTO_ACOMP2
	select ZSTD_COMPRESS
	select ZSTD_DECOMPRESS
	help
	  zstd compression algorithm

	  See https://github.com/facebook/zstd for further information.

endmenu

menu "Random number generation"

config CRYPTO_ANSI_CPRNG
	tristate "ANSI PRNG (Pseudo Random Number Generator)"
	select CRYPTO_AES
	select CRYPTO_RNG
	help
	  Pseudo RNG (random number generator) (ANSI X9.31 Appendix A.2.4)

	  This uses the AES cipher algorithm.

	  Note that this option must be enabled if CRYPTO_FIPS is selected

menuconfig CRYPTO_DRBG_MENU
	tristate "NIST SP800-90A DRBG (Deterministic Random Bit Generator)"
	help
	  DRBG (Deterministic Random Bit Generator) (NIST SP800-90A)

	  In the following submenu, one or more of the DRBG types must be selected.

if CRYPTO_DRBG_MENU

config CRYPTO_DRBG_HMAC
	bool
	default y
	select CRYPTO_HMAC
	select CRYPTO_SHA512

config CRYPTO_DRBG_HASH
	bool "Hash_DRBG"
	select CRYPTO_SHA256
	help
	  Hash_DRBG variant as defined in NIST SP800-90A.

	  This uses the SHA-1, SHA-256, SHA-384, or SHA-512 hash algorithms.

config CRYPTO_DRBG_CTR
	bool "CTR_DRBG"
	select CRYPTO_AES
	select CRYPTO_CTR
	help
	  CTR_DRBG variant as defined in NIST SP800-90A.

	  This uses the AES cipher algorithm with the counter block mode.

config CRYPTO_DRBG
	tristate
	default CRYPTO_DRBG_MENU
	select CRYPTO_RNG
	select CRYPTO_JITTERENTROPY

endif	# if CRYPTO_DRBG_MENU

config CRYPTO_JITTERENTROPY
	tristate "CPU Jitter Non-Deterministic RNG (Random Number Generator)"
	select CRYPTO_RNG
	select CRYPTO_SHA3
	help
	  CPU Jitter RNG (Random Number Generator) from the Jitterentropy library

	  A non-physical non-deterministic ("true") RNG (e.g., an entropy source
	  compliant with NIST SP800-90B) intended to provide a seed to a
	  deterministic RNG (e.g., per NIST SP800-90C).
	  This RNG does not perform any cryptographic whitening of the generated
	  random numbers.

	  See https://www.chronox.de/jent/

if CRYPTO_JITTERENTROPY
if CRYPTO_FIPS && EXPERT

choice
	prompt "CPU Jitter RNG Memory Size"
	default CRYPTO_JITTERENTROPY_MEMSIZE_2
	help
	  The Jitter RNG measures the execution time of memory accesses.
	  Multiple consecutive memory accesses are performed. If the memory
	  size fits into a cache (e.g. L1), only the memory access timing
	  to that cache is measured. The closer the cache is to the CPU
	  the less variations are measured and thus the less entropy is
	  obtained. Thus, if the memory size fits into the L1 cache, the
	  obtained entropy is less than if the memory size fits within
	  L1 + L2, which in turn is less if the memory fits into
	  L1 + L2 + L3. Thus, by selecting a different memory size,
	  the entropy rate produced by the Jitter RNG can be modified.

	config CRYPTO_JITTERENTROPY_MEMSIZE_2
		bool "2048 Bytes (default)"

	config CRYPTO_JITTERENTROPY_MEMSIZE_128
		bool "128 kBytes"

	config CRYPTO_JITTERENTROPY_MEMSIZE_1024
		bool "1024 kBytes"

	config CRYPTO_JITTERENTROPY_MEMSIZE_8192
		bool "8192 kBytes"
endchoice

config CRYPTO_JITTERENTROPY_MEMORY_BLOCKS
	int
	default 64 if CRYPTO_JITTERENTROPY_MEMSIZE_2
	default 512 if CRYPTO_JITTERENTROPY_MEMSIZE_128
	default 1024 if CRYPTO_JITTERENTROPY_MEMSIZE_1024
	default 4096 if CRYPTO_JITTERENTROPY_MEMSIZE_8192

config CRYPTO_JITTERENTROPY_MEMORY_BLOCKSIZE
	int
	default 32 if CRYPTO_JITTERENTROPY_MEMSIZE_2
	default 256 if CRYPTO_JITTERENTROPY_MEMSIZE_128
	default 1024 if CRYPTO_JITTERENTROPY_MEMSIZE_1024
	default 2048 if CRYPTO_JITTERENTROPY_MEMSIZE_8192

config CRYPTO_JITTERENTROPY_OSR
	int "CPU Jitter RNG Oversampling Rate"
	range 1 15
	default 1
	help
	  The Jitter RNG allows the specification of an oversampling rate (OSR).
	  The Jitter RNG operation requires a fixed amount of timing
	  measurements to produce one output block of random numbers. The
	  OSR value is multiplied with the amount of timing measurements to
	  generate one output block. Thus, the timing measurement is oversampled
	  by the OSR factor. The oversampling allows the Jitter RNG to operate
	  on hardware whose timers deliver limited amount of entropy (e.g.
	  the timer is coarse) by setting the OSR to a higher value. The
	  trade-off, however, is that the Jitter RNG now requires more time
	  to generate random numbers.

config CRYPTO_JITTERENTROPY_TESTINTERFACE
	bool "CPU Jitter RNG Test Interface"
	help
	  The test interface allows a privileged process to capture
	  the raw unconditioned high resolution time stamp noise that
	  is collected by the Jitter RNG for statistical analysis. As
	  this data is used at the same time to generate random bits,
	  the Jitter RNG operates in an insecure mode as long as the
	  recording is enabled. This interface therefore is only
	  intended for testing purposes and is not suitable for
	  production systems.

	  The raw noise data can be obtained using the jent_raw_hires
	  debugfs file. Using the option
	  jitterentropy_testing.boot_raw_hires_test=1 the raw noise of
	  the first 1000 entropy events since boot can be sampled.

	  If unsure, select N.

endif	# if CRYPTO_FIPS && EXPERT

if !(CRYPTO_FIPS && EXPERT)

config CRYPTO_JITTERENTROPY_MEMORY_BLOCKS
	int
	default 64

config CRYPTO_JITTERENTROPY_MEMORY_BLOCKSIZE
	int
	default 32

config CRYPTO_JITTERENTROPY_OSR
	int
	default 1

config CRYPTO_JITTERENTROPY_TESTINTERFACE
	bool

endif	# if !(CRYPTO_FIPS && EXPERT)
endif	# if CRYPTO_JITTERENTROPY

config CRYPTO_KDF800108_CTR
	tristate
	select CRYPTO_HMAC
	select CRYPTO_SHA256

endmenu
menu "Userspace interface"

config CRYPTO_USER_API
	tristate

config CRYPTO_USER_API_HASH
	tristate "Hash algorithms"
	depends on NET
	select CRYPTO_HASH
	select CRYPTO_USER_API
	help
	  Enable the userspace interface for hash algorithms.

	  See Documentation/crypto/userspace-if.rst and
	  https://www.chronox.de/libkcapi/html/index.html

config CRYPTO_USER_API_SKCIPHER
	tristate "Symmetric key cipher algorithms"
	depends on NET
	select CRYPTO_SKCIPHER
	select CRYPTO_USER_API
	help
	  Enable the userspace interface for symmetric key cipher algorithms.

	  See Documentation/crypto/userspace-if.rst and
	  https://www.chronox.de/libkcapi/html/index.html

config CRYPTO_USER_API_RNG
	tristate "RNG (random number generator) algorithms"
	depends on NET
	select CRYPTO_RNG
	select CRYPTO_USER_API
	help
	  Enable the userspace interface for RNG (random number generator)
	  algorithms.

	  See Documentation/crypto/userspace-if.rst and
	  https://www.chronox.de/libkcapi/html/index.html

config CRYPTO_USER_API_RNG_CAVP
	bool "Enable CAVP testing of DRBG"
	depends on CRYPTO_USER_API_RNG && CRYPTO_DRBG
	help
	  Enable extra APIs in the userspace interface for NIST CAVP
	  (Cryptographic Algorithm Validation Program) testing:
	  - resetting DRBG entropy
	  - providing Additional Data

	  This should only be enabled for CAVP testing. You should say
	  no unless you know what this is.

config CRYPTO_USER_API_AEAD
	tristate "AEAD cipher algorithms"
	depends on NET
	select CRYPTO_AEAD
	select CRYPTO_SKCIPHER
	select CRYPTO_NULL
	select CRYPTO_USER_API
	help
	  Enable the userspace interface for AEAD cipher algorithms.

	  See Documentation/crypto/userspace-if.rst and
	  https://www.chronox.de/libkcapi/html/index.html

config CRYPTO_USER_API_ENABLE_OBSOLETE
	bool "Obsolete cryptographic algorithms"
	depends on CRYPTO_USER_API
	default y
	help
	  Allow obsolete cryptographic algorithms to be selected that have
	  already been phased out from internal use by the kernel, and are
	  only useful for userspace clients that still rely on them.

endmenu

config CRYPTO_HASH_INFO
	bool

if !KMSAN # avoid false positives from assembly
if ARM
source "arch/arm/crypto/Kconfig"
endif
if ARM64
source "arch/arm64/crypto/Kconfig"
endif
if LOONGARCH
source "arch/loongarch/crypto/Kconfig"
endif
if MIPS
source "arch/mips/crypto/Kconfig"
endif
if PPC
source "arch/powerpc/crypto/Kconfig"
endif
if RISCV
source "arch/riscv/crypto/Kconfig"
endif
if S390
source "arch/s390/crypto/Kconfig"
endif
if SPARC
source "arch/sparc/crypto/Kconfig"
endif
if X86
source "arch/x86/crypto/Kconfig"
endif
endif

source "drivers/crypto/Kconfig"
source "crypto/asymmetric_keys/Kconfig"
source "certs/Kconfig"

endif	# if CRYPTO