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KECCAK-KMAC-128 and KECCAK-KMAC-256 are extendable output functions that have been defined because they are convenient for implementing KMAC. Give definitions for them so that users aren't left to figure that out themselves. KECCAK-KMAC-128 is very similar to SHAKE-128, and KECCAK-KMAC-256 is very similar to SHAKE-256. Related to #22619. Reviewed-by: Neil Horman <nhorman@openssl.org> Reviewed-by: Shane Lontis <shane.lontis@oracle.com> Reviewed-by: Tomas Mraz <tomas@openssl.org> Reviewed-by: Richard Levitte <levitte@openssl.org> (Merged from https://github.com/openssl/openssl/pull/22755)
102 lines
3.1 KiB
Plaintext
102 lines
3.1 KiB
Plaintext
=pod
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=head1 NAME
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EVP_MD-SHAKE, EVP_MD-KECCAK-KMAC
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- The SHAKE / KECCAK family EVP_MD implementations
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=head1 DESCRIPTION
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Support for computing SHAKE or KECCAK-KMAC digests through the
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B<EVP_MD> API.
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KECCAK-KMAC is an Extendable Output Function (XOF), with a definition
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similar to SHAKE, used by the KMAC EVP_MAC implementation (see
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L<EVP_MAC-KMAC(7)>).
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=head2 Identities
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This implementation is available in the FIPS provider as well as the default
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provider, and includes the following varieties:
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=over 4
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=item KECCAK-KMAC-128
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Known names are "KECCAK-KMAC-128" and "KECCAK-KMAC128". This is used
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by L<EVP_MAC-KMAC128(7)>. Using the notation from NIST FIPS 202
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(Section 6.2), we have KECCAK-KMAC-128(M, d) = KECCAK[256](M || 00, d)
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(see the description of KMAC128 in Appendix A of NIST SP 800-185).
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=item KECCAK-KMAC-256
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Known names are "KECCAK-KMAC-256" and "KECCAK-KMAC256". This is used
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by L<EVP_MAC-KMAC256(7)>. Using the notation from NIST FIPS 202
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(Section 6.2), we have KECCAK-KMAC-256(M, d) = KECCAK[512](M || 00, d)
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(see the description of KMAC256 in Appendix A of NIST SP 800-185).
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=item SHAKE-128
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Known names are "SHAKE-128" and "SHAKE128".
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=item SHAKE-256
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Known names are "SHAKE-256" and "SHAKE256".
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=back
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=head2 Gettable Parameters
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This implementation supports the common gettable parameters described
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in L<EVP_MD-common(7)>.
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=head2 Settable Context Parameters
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These implementations support the following L<OSSL_PARAM(3)> entries,
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settable for an B<EVP_MD_CTX> with L<EVP_MD_CTX_set_params(3)>:
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=over 4
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=item "xoflen" (B<OSSL_DIGEST_PARAM_XOFLEN>) <unsigned integer>
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Sets the digest length for extendable output functions.
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The length of the "xoflen" parameter should not exceed that of a B<size_t>.
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For backwards compatibility reasons the default xoflen length for SHAKE-128 is
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16 (bytes) which results in a security strength of only 64 bits. To ensure the
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maximum security strength of 128 bits, the xoflen should be set to at least 32.
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For backwards compatibility reasons the default xoflen length for SHAKE-256 is
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32 (bytes) which results in a security strength of only 128 bits. To ensure the
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maximum security strength of 256 bits, the xoflen should be set to at least 64.
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This parameter may be used when calling either EVP_DigestFinal_ex() or
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EVP_DigestFinal(), since these functions were not designed to handle variable
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length output. It is recommended to either use EVP_DigestSqueeze() or
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EVP_DigestFinalXOF() instead.
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=back
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=head1 NOTES
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For SHAKE-128, to ensure the maximum security strength of 128 bits, the output
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length passed to EVP_DigestFinalXOF() should be at least 32.
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For SHAKE-256, to ensure the maximum security strength of 256 bits, the output
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length passed to EVP_DigestFinalXOF() should be at least 64.
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=head1 SEE ALSO
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L<EVP_MD_CTX_set_params(3)>, L<provider-digest(7)>, L<OSSL_PROVIDER-default(7)>
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=head1 COPYRIGHT
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Copyright 2020-2023 The OpenSSL Project Authors. All Rights Reserved.
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Licensed under the Apache License 2.0 (the "License"). You may not use
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this file except in compliance with the License. You can obtain a copy
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in the file LICENSE in the source distribution or at
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L<https://www.openssl.org/source/license.html>.
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=cut
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