=pod

=encoding utf8

=head1 NAME

sm3_hmac_init, sm3_hmac_update, sm3_hmac_final, sm3_hmac - SM3 Hash Algorithm

=head1 SYNOPSIS

 #include <openssl/sm3.h>

 void sm3_hmac_init(sm3_hmac_ctx_t *ctx, const unsigned char *key, size_t key_len);
 void sm3_hmac_update(sm3_hmac_ctx_t *ctx, const unsigned char *data, size_t data_len);
 void sm3_hmac_final(sm3_hmac_ctx_t *ctx, unsigned char mac[SM3_HMAC_SIZE]);
 void sm3_hmac(const unsigned char *data, size_t data_len,
	const unsigned char *key, size_t key_len, unsigned char mac[SM3_HMAC_SIZE]);

=head1 DESCRIPTION

Applications should use the higher level functions
L<HMAC_Init(3)> etc. instead of calling the hash
functions directly.

sm3_hmac() computes the SM3 message digest of the B<n>
bytes at B<d> and places it in B<md> (which must have space for
SHA_DIGEST_LENGTH == 20 bytes of output). If B<md> is NULL, the digest
is placed in a static array. Note: setting B<md> to NULL is B<not thread safe>.

The following functions may be used if the message is not completely
stored in memory:

sm3_hmac_init() initializes a B<sm3_ctx_t> structure.

sm3_hmac_update() can be called repeatedly with chunks of the message to
be hashed (B<len> bytes at B<data>).

sm3_hmac_final() places the message digest in B<md>, which must have space
for SM3_DIGEST_LENGTH == 32 bytes of output, and erases the B<sm3_hmac_ctx_t>.

=head1 RETURN VALUES

sm3_init(), sm3_update(), sm3_final(), sm3_compress() and sm3() return void.

=head1 CONFORMING TO

GM/T 0004-2012 SM3 Cryptogrpahic Hash Algorithm.

=head1 SEE ALSO

L<HMAC_Init(3)>

=head1 COPYRIGHT

Copyright 2014-2019 The GmSSL Project. All Rights Reserved.

Licensed under the GmSSL license (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<http://gmssl.org/license.html>.

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