=pod

=encoding utf8

=head1 NAME

OTP_generate - One-Time Password Algorithm

=head1 SYNOPSIS

 #include <openssl/otp.h>

 typedef struct OTP_PARAMS_st {
	int type;
	int te;
	void *option;
	size_t option_size;
	int otp_digits;
	/* adjust the clock in seconds */
	int offset;
 } OTP_PARAMS;

 int OTP_generate(const OTP_PARAMS *params,
                  const void *event, size_t eventlen,
                  unsigned int *otp,
                  const unsigned char *key, size_t keylen);

=head1 DESCRIPTION

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

SM3 (ShangMi#3 Hash Algorithm) is a cryptographic hash function with a
256 bit output.

sm3() 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_nit() initializes a B<sm3_ctx_t> structure.

sm3_update() can be called repeatedly with chunks of the message to
be hashed (B<len> bytes at B<data>).

sm3_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_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<EVP_DigestInit(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>.

=cut