=pod

=head1 NAME

EVP_MAC_BLAKE2 - The BLAKE2 EVP_MAC implementation

=head1 DESCRIPTION

Support for computing BLAKE2 MACs through the B<EVP_MAC> API.

=head2 Numeric identity

B<EVP_MAC_BLAKE2B> and B<EVP_MAC_BLAKE2S> are the numeric identities 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>

This is a string value of at most 64 bytes for EVP_MAC_BLAKE2B
or 32 for EVP_MAC_BLAKE2S and at least 1 byte in both cases.
This must be set before calling EVP_MAC_init().

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_CUSTOM>

This is an optional string value of at most 16 bytes for EVP_MAC_BLAKE2B
or 8 for EVP_MAC_BLAKE2S, set to all-NULL by default.
If used this must be set before calling EVP_MAC_init().

EVP_MAC_ctrl_str() takes two type strings for this control:

=over 4

=item "custom"

The value string is used as is.

=item "hexcustom"

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_SALT>

This is an optional string value of at most 16 bytes for EVP_MAC_BLAKE2B
or 8 for EVP_MAC_BLAKE2S, set to all-NULL by default.
If used this must be set before calling EVP_MAC_init().

EVP_MAC_ctrl_str() takes two type strings for this control:

=over 4

=item "salt"

The value string is used as is.

=item "hexsalt"

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_SIZE>

EVP_MAC_ctrl_str() type string: "outlen"

This is an optional value string containing a decimal number between 1 and
32 for EVP_MAC_BLAKE2S or 64 for EVP_MAC_BLAKE2B.
If it is not set it uses the default digest size of 32 and 64 respectively.
If used this must be set before calling EVP_MAC_init().

=back

=head1 SEE ALSO

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

=head1 HISTORY

The macros and functions described here were added to OpenSSL 3.0.0.

=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>.

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