mirror of https://github.com/openssl/openssl
102 lines
2.9 KiB
Plaintext
102 lines
2.9 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 S<KECCAK-KMAC-128(M, d)> = S<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 S<KECCAK-KMAC-256(M, d)> = S<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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The SHAKE-128 and SHAKE-256 implementations do not have any default digest
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length.
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This parameter must be set before 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 HISTORY
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Since OpenSSL 3.4 the SHAKE-128 and SHAKE-256 implementations have no default
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digest length.
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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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