=pod

=head1 NAME

MD2, MD4, MD5, MD2_Init, MD2_Update, MD2_Final, MD4_Init, MD4_Update,
MD4_Final, MD5_Init, MD5_Update, MD5_Final - MD2, MD4, and MD5 hash functions

=head1 SYNOPSIS

 #include <openssl/md2.h>

 unsigned char *MD2(const unsigned char *d, unsigned long n, unsigned char *md);

 int MD2_Init(MD2_CTX *c);
 int MD2_Update(MD2_CTX *c, const unsigned char *data, unsigned long len);
 int MD2_Final(unsigned char *md, MD2_CTX *c);


 #include <openssl/md4.h>

 unsigned char *MD4(const unsigned char *d, unsigned long n, unsigned char *md);

 int MD4_Init(MD4_CTX *c);
 int MD4_Update(MD4_CTX *c, const void *data, unsigned long len);
 int MD4_Final(unsigned char *md, MD4_CTX *c);


 #include <openssl/md5.h>

 unsigned char *MD5(const unsigned char *d, unsigned long n, unsigned char *md);

 int MD5_Init(MD5_CTX *c);
 int MD5_Update(MD5_CTX *c, const void *data, unsigned long len);
 int MD5_Final(unsigned char *md, MD5_CTX *c);

=head1 DESCRIPTION

MD2, MD4, and MD5 are cryptographic hash functions with a 128 bit output.

MD2(), MD4(), and MD5() compute the MD2, MD4, and MD5 message digest
of the B<n> bytes at B<d> and place it in B<md> (which must have space
for MD2_DIGEST_LENGTH == MD4_DIGEST_LENGTH == MD5_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:

MD2_Init() initializes a B<MD2_CTX> structure.

MD2_Update() can be called repeatedly with chunks of the message to
be hashed (B<len> bytes at B<data>).

MD2_Final() places the message digest in B<md>, which must have space
for MD2_DIGEST_LENGTH == 16 bytes of output, and erases the B<MD2_CTX>.

MD4_Init(), MD4_Update(), MD4_Final(), MD5_Init(), MD5_Update(), and
MD5_Final() are analogous using an B<MD4_CTX> and B<MD5_CTX> structure.

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

=head1 NOTE

MD2, MD4, and MD5 are recommended only for compatibility with existing
applications. In new applications, SHA-1 or RIPEMD-160 should be
preferred.

=head1 RETURN VALUES

MD2(), MD4(), and MD5() return pointers to the hash value.

MD2_Init(), MD2_Update(), MD2_Final(), MD4_Init(), MD4_Update(),
MD4_Final(), MD5_Init(), MD5_Update(), and MD5_Final() return 1 for
success, 0 otherwise.

=head1 CONFORMING TO

RFC 1319, RFC 1320, RFC 1321

=head1 SEE ALSO

L<EVP_DigestInit(3)>

=head1 COPYRIGHT

Copyright 2000-2016 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
