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EVP_MD-SHAKE(7SSL)                             OpenSSL                            EVP_MD-SHAKE(7SSL)

NAME
       EVP_MD-SHAKE, EVP_MD-KECCAK-KMAC - The SHAKE / KECCAK family EVP_MD implementations

DESCRIPTION
       Support for computing SHAKE or KECCAK-KMAC digests through the EVP_MD API.

       KECCAK-KMAC is an Extendable Output Function (XOF), with a definition similar to SHAKE, used
       by the KMAC EVP_MAC implementation (see EVP_MAC-KMAC(7)).

   Identities
       This implementation is available in the FIPS provider as well as the default provider, and
       includes the following varieties:

       KECCAK-KMAC-128
           Known   names   are   "KECCAK-KMAC-128"   and   "KECCAK-KMAC128".    This   is   used  by
           EVP_MAC-KMAC128(7).  Using the notation  from  NIST  FIPS  202  (Section  6.2),  we  have
           KECCAK-KMAC-128(M, d)  =  KECCAK[256](M || 00, d)  (see  the  description  of  KMAC128 in
           Appendix A of NIST SP 800-185).

       KECCAK-KMAC-256
           Known  names   are   "KECCAK-KMAC-256"   and   "KECCAK-KMAC256".    This   is   used   by
           EVP_MAC-KMAC256(7).   Using  the  notation  from  NIST  FIPS  202  (Section 6.2), we have
           KECCAK-KMAC-256(M, d) =  KECCAK[512](M || 00, d)  (see  the  description  of  KMAC256  in
           Appendix A of NIST SP 800-185).

       SHAKE-128
           Known names are "SHAKE-128" and "SHAKE128".

       SHAKE-256
           Known names are "SHAKE-256" and "SHAKE256".

   Gettable Parameters
       This implementation supports the common gettable parameters described in EVP_MD-common(7).

   Settable Context Parameters
       These implementations support the following OSSL_PARAM(3) entries, settable for an EVP_MD_CTX
       with EVP_MD_CTX_set_params(3):

       "xoflen" (OSSL_DIGEST_PARAM_XOFLEN) <unsigned integer>
           Sets  the  digest  length  for  extendable  output functions.  The length of the "xoflen"
           parameter should not exceed that of a size_t.

           For backwards compatibility reasons the default xoflen length for SHAKE-128 is 16 (bytes)
           which results in a security strength of only 64 bits.  To  ensure  the  maximum  security
           strength of 128 bits, the xoflen should be set to at least 32.

           For backwards compatibility reasons the default xoflen length for SHAKE-256 is 32 (bytes)
           which  results  in  a  security strength of only 128 bits. To ensure the maximum security
           strength of 256 bits, the xoflen should be set to at least 64.

SEE ALSO
       EVP_MD_CTX_set_params(3), provider-digest(7), OSSL_PROVIDER-default(7)

COPYRIGHT
       Copyright 2020-2022 The OpenSSL Project Authors. All Rights Reserved.

       Licensed under the Apache License 2.0 (the "License").  You may not use this file  except  in
       compliance  with  the  License.   You  can  obtain  a  copy in the file LICENSE in the source
       distribution or at <https://www.openssl.org/source/license.html>.

3.0.13                                       2026-07-29                           EVP_MD-SHAKE(7SSL)