| 1 | =pod
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| 2 |
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| 3 | =head1 NAME
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| 4 |
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| 5 | EVP_MD-SHAKE, EVP_MD-KECCAK-KMAC
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| 6 | - The SHAKE / KECCAK family EVP_MD implementations
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| 7 |
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| 8 | =head1 DESCRIPTION
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| 9 |
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| 10 | Support for computing SHAKE or KECCAK-KMAC digests through the
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| 11 | B<EVP_MD> API.
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| 12 |
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| 13 | KECCAK-KMAC is an Extendable Output Function (XOF), with a definition
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| 14 | similar to SHAKE, used by the KMAC EVP_MAC implementation (see
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| 15 | L<EVP_MAC-KMAC(7)>).
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| 16 |
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| 17 | =head2 Identities
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| 18 |
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| 19 | This implementation is available in the FIPS provider as well as the default
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| 20 | provider, and includes the following varieties:
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| 21 |
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| 22 | =over 4
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| 23 |
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| 24 | =item KECCAK-KMAC-128
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| 25 |
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| 26 | Known names are "KECCAK-KMAC-128" and "KECCAK-KMAC128". This is used
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| 27 | by L<EVP_MAC-KMAC128(7)>. Using the notation from NIST FIPS 202
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| 28 | (Section 6.2), we have S<KECCAK-KMAC-128(M, d)> = S<KECCAK[256](M || 00, d)>
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| 29 | (see the description of KMAC128 in Appendix A of NIST SP 800-185).
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| 30 |
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| 31 | =item KECCAK-KMAC-256
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| 32 |
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| 33 | Known names are "KECCAK-KMAC-256" and "KECCAK-KMAC256". This is used
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| 34 | by L<EVP_MAC-KMAC256(7)>. Using the notation from NIST FIPS 202
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| 35 | (Section 6.2), we have S<KECCAK-KMAC-256(M, d)> = S<KECCAK[512](M || 00, d)>
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| 36 | (see the description of KMAC256 in Appendix A of NIST SP 800-185).
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| 37 |
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| 38 | =item SHAKE-128
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| 39 |
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| 40 | Known names are "SHAKE-128" and "SHAKE128".
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| 41 |
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| 42 | =item SHAKE-256
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| 43 |
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| 44 | Known names are "SHAKE-256" and "SHAKE256".
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| 45 |
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| 46 | =back
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| 47 |
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| 48 | =head2 Gettable Parameters
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| 49 |
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| 50 | This implementation supports the common gettable parameters described
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| 51 | in L<EVP_MD-common(7)>.
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| 52 |
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| 53 | =head2 Settable Context Parameters
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| 54 |
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| 55 | These implementations support the following L<OSSL_PARAM(3)> entries,
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| 56 | settable for an B<EVP_MD_CTX> with L<EVP_MD_CTX_set_params(3)>:
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| 57 |
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| 58 | =over 4
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| 59 |
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| 60 | =item "xoflen" (B<OSSL_DIGEST_PARAM_XOFLEN>) <unsigned integer>
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| 61 |
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| 62 | Sets the digest length for extendable output functions.
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| 63 | The length of the "xoflen" parameter should not exceed that of a B<size_t>.
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| 64 |
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| 65 | For backwards compatibility reasons the default xoflen length for SHAKE-128 is
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| 66 | 16 (bytes) which results in a security strength of only 64 bits. To ensure the
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| 67 | maximum security strength of 128 bits, the xoflen should be set to at least 32.
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| 68 |
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| 69 | For backwards compatibility reasons the default xoflen length for SHAKE-256 is
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| 70 | 32 (bytes) which results in a security strength of only 128 bits. To ensure the
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| 71 | maximum security strength of 256 bits, the xoflen should be set to at least 64.
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| 72 |
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| 73 | =back
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| 74 |
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| 75 | =head1 SEE ALSO
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| 76 |
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| 77 | L<EVP_MD_CTX_set_params(3)>, L<provider-digest(7)>, L<OSSL_PROVIDER-default(7)>
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| 78 |
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| 79 | =head1 COPYRIGHT
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| 80 |
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| 81 | Copyright 2020-2022 The OpenSSL Project Authors. All Rights Reserved.
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| 82 |
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| 83 | Licensed under the Apache License 2.0 (the "License"). You may not use
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| 84 | this file except in compliance with the License. You can obtain a copy
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| 85 | in the file LICENSE in the source distribution or at
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| 86 | L<https://www.openssl.org/source/license.html>.
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| 87 |
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| 88 | =cut
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