hash/rmd160/rmd160.3

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.\" Copyright (c) 1997 Todd C. Miller <Todd.Miller@courtesan.com>
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.\" See http://www.esat.kuleuven.ac.be/~bosselae/ripemd160.html
.\"	for detailed information about RIPEMD-160.
.\"
.Dd July 16, 1997
.Dt RMD160 3
.Os
.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
.In sys/types.h
.In 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 "uint32_t state[5]" "const uint32_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" "size_t 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(\*[Am]rmd);
RMD160Update(\*[Am]rmd, (u_char *)buf, n);
RMD160Final(results, \*[Am]rmd);

/* Print the digest as one long hex value */
printf("0x");
for (n = 0; n \*[Lt] 20; n++)
	printf("%02x", results[n]);
putchar('\en');
.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\en", RMD160Data(buf, strlen(buf), output));
.Ed
.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
.Ox 2.1 .
.Sh AUTHORS
This implementation of RMD-160 was written by Antoon Bosselaers.
.Pp
The
.Fn RMD160End ,
.Fn RMD160File ,
and
.Fn RMD160Data
helper functions are derived from code written by Poul-Henning Kamp.
.Sh BUGS
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.