.\"	$OpenBSD: rmd160.3,v 1.2 1997/07/17 06:05:40 millert Exp $
.\"
.\" Copyright (c) 1997 Todd C. Miller <Todd.Miller@courtesan.com>
.\" All rights reserved.
.\"
.\" Redistribution and use in source and binary forms, with or without
.\" modification, are permitted provided that the following conditions
.\" are met:
.\" 1. Redistributions of source code must retain the above copyright
.\"    notice, this list of conditions and the following disclaimer.
.\" 2. Redistributions in binary form must reproduce the above copyright
.\"    notice, this list of conditions and the following disclaimer in the
.\"    documentation and/or other materials provided with the distribution.
.\" 3. All advertising materials mentioning features or use of this software
.\"    must display the following acknowledgement:
.\"	This product includes software developed by Todd C. Miller.
.\" 4. The name of the author may not be used to endorse or promote products
.\"    derived from this software without specific prior written permission.
.\"
.\" THIS SOFTWARE IS PROVIDED ``AS IS'' AND ANY EXPRESS OR IMPLIED WARRANTIES,
.\" INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY
.\" AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.  IN NO EVENT SHALL
.\" THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL,
.\" EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO,
.\" PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS;
.\" OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY,
.\" WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR
.\" OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF
.\" ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
.\"
.\" See http://www.esat.kuleuven.ac.be/~bosselae/ripemd160.html
.\"	for detailed information about RIPEMD-160.
.\"
.Dd July 16, 1997
.Dt RMD160 3
.Sh NAME
.Nm RMD160Init ,
.Nm RMD160Update ,
.Nm RMD160Final ,
.Nm RMD160Transform ,
.Nm RMD160End ,
.Nm RMD160File ,
.Nm RMD160Data ,
.Nd calculate the ``RIPEMD-160'' message digest
.Sh SYNOPSIS
.Fd #include <sys/types.h>
.Fd #include <rmd160.h>
.Ft void
.Fn RMD160Init "RMD160_CTX *context"
.Ft void
.Fn RMD160Update "RMD160_CTX *context" "const u_char *data" "u_int nbytes"
.Ft void
.Fn RMD160Final "u_char digest[20]" "RMD160_CTX *context"
.Ft void
.Fn RMD160Transform "u_int32_t state[5]" "const u_int32_t block[16]"
.Ft "char *"
.Fn RMD160End "RMD160_CTX *context" "char *buf"
.Ft "char *"
.Fn RMD160File "char *filename" "char *buf"
.Ft "char *"
.Fn RMD160Data "u_char *data" "u_int len" "char *buf"
.Sh DESCRIPTION
The RMD160 functions implement the 160-bit RIPE message digest hash algorithm
(RMD-160).  RMD-160 is used to generate a condensed representation
of a message called a message digest.  The algorithm takes a
message less than 2^64 bits as input and produces a 160-bit digest
suitable for use as a digital signature.
.Pp
The RMD160 functions are considered to be more secure than the 
.Xr md4 3
and
.Xr md5 3
functions and at least as secure as the
.Xr sha1 3
function.  All share a similar interface.
.Pp
The
.Fn RMD160Init
function initializes a RMD160_CTX
.Ar context
for use with
.Fn RMD160Update ,
and
.Fn RMD160Final .
The
.Fn RMD160Update
function adds
.Ar data
of length
.Ar nbytes
to the RMD160_CTX specified by
.Ar context.
.Fn RMD160Final
is called when all data has been added via
.Fn RMD160Update
and stores a message digest in the
.Ar digest
parameter.
When a null pointer is passed to
.Fn RMD160Final
as first argument only the final padding will be applied and the 
current context can still be used with
.Fn RMD160Update .
.Pp
The
.Fn RMD160Transform
function is used by
.Fn RMD160Update
to hash 512-bit blocks and forms the core of the algorithm.
Most programs should use the interface provided by
.Fn RMD160Init ,
.Fn RMD160Update
and
.Fn RMD160Final
instead of calling
.Fn RMD160Transform
directly.
.Pp
The
.Fn RMD160End
function is a front end for
.Fn RMD160Final
which converts the digest into an
.Tn ASCII
representation of the 160 bit digest in hexadecimal.
.Pp
The
.Fn RMD160File
function calculates the digest for a file and returns the result via
.Fn RMD160End .
If
.Fn RMD160File
is unable to open the file a NULL pointer is returned.
.Pp
The
.Fn RMD160Data
function
calculates the digest of an arbitrary string and returns the result via
.Fn RMD160End .
.Pp
For each of the
.Fn RMD160End ,
.Fn RMD160File ,
and
.Fn RMD160Data
functions the
.Ar buf
parameter should either be a string of at least 41 characters in
size or a NULL pointer.  In the latter case, space will be dynamically
allocated via
.Xr malloc 3
and should be freed using
.Xr free 3
when it is no longer needed.
.Sh EXAMPLES
The follow code fragment will calculate the digest for
the string "abc" which is ``0x8eb208f7e05d987a9b044a8e98c6b087f15a0bfc''.
.Bd -literal -offset indent
RMD160_CTX rmd;
u_char results[20];
char *buf;
int n;

buf = "abc";
n = strlen(buf);
RMD160Init(&rmd);
RMD160Update(&rmd, (u_char *)buf, n);
RMD160Final(results, &rmd);

/* Print the digest as one long hex value */
printf("0x");
for (n = 0; n < 20; n++)
	printf("%x", results[n]);
putchar('\\n');
.Ed
.Pp
Alternately, the helper functions could be used in the following way:
.Bd -literal -offset indent
RMD160_CTX rmd;
u_char output[41];
char *buf = "abc";

printf("0x%s", RMD160Data(buf, strlen(buf), output));
.Ed
.Sh CAVEATS
If a message digest is to be copied to a multi-byte type (ie:
an array of five 32-bit integers) it will be necessary to
perform byte swapping on little endian machines such as the i386, alpha,
and vax.
.Sh AUTHOR
This implementation of RMD-160 was written by Antoon Bosselaers.
.br
The
.Fn RMD160End ,
.Fn RMD160File ,
and
.Fn RMD160Data
helper functions are derived from code written by Poul-Henning Kamp.
.Sh SEE ALSO
.Xr rmd160 1 ,
.Xr md4 3 ,
.Xr md5 3 ,
.Xr sha1 3
.Pp
.Rs
.%A H. Dobbertin, A. Bosselaers, B. Preneel
.%T RIPEMD-160, a strengthened version of RIPEMD
.Re
.Rs
.%T Information technology - Security techniques - Hash-functions - Part 3: Dedicated hash-functions
.%O ISO/IEC 10118-3
.Re
.Rs
.%A H. Dobbertin, A. Bosselaers, B. Preneel
.%T The RIPEMD-160 cryptographic hash function
.%J Dr. Dobb's Journal
.%V Vol. 22, No. 1
.%D January 1997
.%P pp. 24-28
.Re
.Sh HISTORY
The RMD-160 functions appeared in
.Bx Open
2.1.