RMD160(3) OpenBSD Programmer's Manual RMD160(3)NAME
RMD160Init, RMD160Update, RMD160Pad, RMD160Final, RMD160Transform,
RMD160End, RMD160File, RMD160FileChunk, RMD160Data - calculate the
``RIPEMD-160'' message digest
SYNOPSIS
#include <sys/types.h>
#include <rmd160.h>
void
RMD160Init(RMD160_CTX *context);
void
RMD160Update(RMD160_CTX *context, const u_int8_t *data, u_int32_t
nbytes);
void
RMD160Pad(RMD160_CTX *context);
void
RMD160Final(u_int8_t digest[RMD160_DIGEST_LENGTH], RMD160_CTX *context);
void
RMD160Transform(u_int32_t state[5], const u_int8_t
block[RMD160_BLOCK_LENGTH]);
char *
RMD160End(RMD160_CTX *context, char *buf);
char *
RMD160File(const char *filename, char *buf);
char *
RMD160FileChunk(const char *filename, char *buf, off_t offset, off_t
length);
char *
RMD160Data(const u_int8_t *data, size_t len, char *buf);
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.
The RMD160 functions are considered to be more secure than the md4(3) and
md5(3) functions and at least as secure as the sha1(3) function. All
share a similar interface.
The RMD160Init() function initializes a RMD160_CTX context for use with
RMD160Update(), and RMD160Final(). The RMD160Update() function adds data
of length nbytes to the RMD160_CTX specified by context. RMD160Final()
is called when all data has been added via RMD160Update() and stores a
message digest in the digest parameter.
The RMD160Pad() function can be used to apply padding to the message
digest as in RMD160Final(), but the current context can still be used
with RMD160Update().
The RMD160Transform() function is used by RMD160Update() to hash 512-bit
blocks and forms the core of the algorithm. Most programs should use the
interface provided by RMD160Init(), RMD160Update() and RMD160Final()
instead of calling RMD160Transform() directly.
The RMD160End() function is a front end for RMD160Final() which converts
the digest into an ASCII representation of the 160 bit digest in
hexadecimal.
The RMD160File() function calculates the digest for a file and returns
the result via RMD160End(). If RMD160File() is unable to open the file a
NULL pointer is returned.
RMD160FileChunk() behaves like RMD160File() but calculates the digest
only for that portion of the file starting at offset and continuing for
length bytes or until end of file is reached, whichever comes first. A
zero length can be specified to read until end of file. A negative
length or offset will be ignored.
The RMD160Data() function calculates the digest of an arbitrary string
and returns the result via RMD160End().
For each of the RMD160End(), RMD160File(), and RMD160Data() functions the
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 malloc(3) and should be freed using free(3) when it is no
longer needed.
EXAMPLES
The follow code fragment will calculate the digest for the string "abc"
which is ``0x8eb208f7e05d987a9b044a8e98c6b087f15a0bfc''.
RMD160_CTX rmd;
u_int8_t results[RMD160_DIGEST_LENGTH];
char *buf;
int n;
buf = "abc";
n = strlen(buf);
RMD160Init(&rmd);
RMD160Update(&rmd, (u_int8_t *)buf, n);
RMD160Final(results, &rmd);
/* Print the digest as one long hex value */
printf("0x");
for (n = 0; n < RMD160_DIGEST_LENGTH; n++)
printf("%02x", results[n]);
putchar('\n');
Alternately, the helper functions could be used in the following way:
RMD160_CTX rmd;
u_int8_t output[RMD160_DIGEST_STRING_LENGTH];
char *buf = "abc";
printf("0x%s\n", RMD160Data(buf, strlen(buf), output));
SEE ALSOcksum(1), md4(3), md5(3), sha1(3), sha2(3)
H. Dobbertin, A. Bosselaers, B. Preneel, RIPEMD-160, a strengthened
version of RIPEMD.
Information technology - Security techniques - Hash-functions - Part 3:
Dedicated hash-functions, ISO/IEC 10118-3.
H. Dobbertin, A. Bosselaers, B. Preneel, "The RIPEMD-160 cryptographic
hash function", Dr. Dobb's Journal, Vol. 22, No. 1, pp. 24-28, January
1997.
HISTORY
The RMD-160 functions appeared in OpenBSD 2.1.
AUTHORS
This implementation of RMD-160 was written by Markus Friedl.
The RMD160End(), RMD160File(), RMD160FileChunk(), and RMD160Data() helper
functions are derived from code written by Poul-Henning Kamp.
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.
OpenBSD 4.9 July 13, 2010 OpenBSD 4.9
