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 algo-
     rithm (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 di-
     gest 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() in-
     stead 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 hexadec-
     imal.

     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 on-
     ly 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 allo-
     cated 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 ALSO
     cksum(1), rmd160(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
     Information0 0Information1 1Information2, 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 4.1                     April 29, 2004                               3
