=pod

=head1 NAME

EVP_PKEY-HMAC, EVP_KEYMGMT-HMAC, EVP_PKEY-Siphash, EVP_KEYMGMT-Siphash,
EVP_PKEY-Poly1305, EVP_KEYMGMT-Poly1305, EVP_PKEY-CMAC, EVP_KEYMGMT-CMAC
- EVP_PKEY legacy MAC keytypes and algorithm support

=head1 DESCRIPTION

The B<HMAC> and B<CMAC> key types are implemented in OpenSSL's default and FIPS
providers. Additionally the B<Siphash> and B<Poly1305> key types are implemented
in the default provider. Performing MAC operations via an EVP_PKEY
is considered legacy and are only available for backwards compatibility purposes
and for a restricted set of algorithms. The preferred way of performing MAC
operations is via the EVP_MAC APIs. See L<EVP_MAC_init(3)>.

For further details on using EVP_PKEY based MAC keys see
L<EVP_SIGNATURE-HMAC(7)>, L<EVP_SIGNATURE-Siphash(7)>,
L<EVP_SIGNATURE-Poly1305(7)> or L<EVP_SIGNATURE-CMAC(7)>.

=head2 Common MAC parameters

All the B<MAC> keytypes support the following parameters.

=over 4

=item "priv" (B<OSSL_PKEY_PARAM_PRIV_KEY>) <octet string>

The MAC key value.

=item "properties" (B<OSSL_PKEY_PARAM_PROPERTIES>) <UTF8 string>

A property query string to be used when any algorithms are fetched.

=back

=head2 CMAC parameters

As well as the parameters described above, the B<CMAC> keytype additionally
supports the following parameters.

=over 4

=item "cipher" (B<OSSL_PKEY_PARAM_CIPHER>) <UTF8 string>

The name of a cipher to be used when generating the MAC.

=item "engine" (B<OSSL_PKEY_PARAM_ENGINE>) <UTF8 string>

The name of an engine to be used for the specified cipher (if any).

=back

=head2 Common MAC key generation parameters

MAC key generation is unusual in that no new key is actually generated. Instead
a new provider side key object is created with the supplied raw key value. This
is done for backwards compatibility with previous versions of OpenSSL.

=over 4

=item "priv" (B<OSSL_PKEY_PARAM_PRIV_KEY>) <octet string>

The MAC key value.

=back

=head2 CMAC key generation parameters

In addition to the common MAC key generation parameters, the CMAC key generation
additionally recognises the following.

=over 4

=item "cipher" (B<OSSL_PKEY_PARAM_CIPHER>) <UTF8 string>

The name of a cipher to be used when generating the MAC.

=back

=head1 SEE ALSO

L<EVP_KEYMGMT(3)>, L<EVP_PKEY(3)>, L<provider-keymgmt(7)>

=head1 COPYRIGHT

Copyright 2020 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
L<https://www.openssl.org/source/license.html>.

=cut