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=head1 NAME

MDC2, MDC2_Init, MDC2_Update, MDC2_Final - MDC2 hash function

=head1 SYNOPSIS

 #include <openssl/mdc2.h>

The following functions have been deprecated since OpenSSL 3.0, and can be
hidden entirely by defining B<OPENSSL_API_COMPAT> with a suitable version value,
see L<openssl_user_macros(7)>:

 unsigned char *MDC2(const unsigned char *d, unsigned long n,
                     unsigned char *md);

 int MDC2_Init(MDC2_CTX *c);
 int MDC2_Update(MDC2_CTX *c, const unsigned char *data,
                 unsigned long len);
 int MDC2_Final(unsigned char *md, MDC2_CTX *c);

=head1 DESCRIPTION

All of the functions described on this page are deprecated.
Applications should instead use L<EVP_DigestInit_ex(3)>, L<EVP_DigestUpdate(3)>
and L<EVP_DigestFinal_ex(3)>.

MDC2 is a method to construct hash functions with 128 bit output from
block ciphers.  These functions are an implementation of MDC2 with
DES.

MDC2() computes the MDC2 message digest of the B<n>
bytes at B<d> and places it in B<md> (which must have space for
MDC2_DIGEST_LENGTH == 16 bytes of output). If B<md> is NULL, the digest
is placed in a static array.

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

MDC2_Init() initializes a B<MDC2_CTX> structure.

MDC2_Update() can be called repeatedly with chunks of the message to
be hashed (B<len> bytes at B<data>).

MDC2_Final() places the message digest in B<md>, which must have space
for MDC2_DIGEST_LENGTH == 16 bytes of output, and erases the B<MDC2_CTX>.

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

=head1 RETURN VALUES

MDC2() returns a pointer to the hash value.

MDC2_Init(), MDC2_Update() and MDC2_Final() return 1 for success, 0 otherwise.

=head1 CONFORMING TO

ISO/IEC 10118-2:2000 Hash-Function 2, with DES as the underlying block cipher.

=head1 SEE ALSO

L<EVP_DigestInit(3)>

=head1 HISTORY

All of these functions were deprecated in OpenSSL 3.0.

=head1 COPYRIGHT

Copyright 2000-2020 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>.

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