=pod

=head1 NAME

EVP_MAC_HMAC - The HMAC EVP_MAC implementation

=head1 DESCRIPTION

Support for computing HMAC MACs through the B<EVP_MAC> API.

=head2 Numeric identity

B<EVP_MAC_HMAC> is the numeric identity for this implementation, and
can be used in functions like EVP_MAC_CTX_new_id() and
EVP_get_macbynid().

=head2 Supported controls

The supported controls are:

=over 4

=item B<EVP_MAC_CTRL_SET_KEY>

EVP_MAC_ctrl_str() takes two type strings for this control:

=over 4

=item "key"

The value string is used as is.

=item "hexkey"

The value string is expected to be a hexadecimal number, which will be
decoded before passing on as control value.

=back

=item B<EVP_MAC_CTRL_SET_FLAGS>

Sets HMAC flags.  This is passed directly to HMAC_CTX_set_flags().

There are no corresponding string control types.

=item B<EVP_MAC_CTRL_SET_ENGINE>

=item B<EVP_MAC_CTRL_SET_MD>

These work as described in L<EVP_MAC(3)/CONTROLS>.

EVP_MAC_ctrl_str() type string for B<EVP_MAC_CTRL_SET_MD>: "digest"

The value is expected to be the name of a cipher.

=back

=head1 SEE ALSO

L<EVP_MAC_ctrl(3)>, L<EVP_MAC(3)/CONTROLS>

=head1 COPYRIGHT

Copyright 2018 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