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RMD160

Section: C Library Functions (3)
Index Return to Main Contents

BSD mandoc

NAME

RMD160Init RMD160Update RMD160Pad RMD160Final RMD160Transform RMD160End RMD160File RMD160FileChunk RMD160Data - calculate the ``RIPEM-160'' message digest

LIBRARY

Lb libmd

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 uint8_t *data uint32_t nbytes Ft void Fn RMD160Pad RMD160_CTX *context Ft void Fn RMD160Final uint8_t digest[RMD160_DIGEST_LENGTH] RMD160_CTX *context Ft void Fn RMD160Transform uint32_t state[5] const uint8_t block[RMD160_BLOCK_LENGTH] Ft char * Fn RMD160End RMD160_CTX *context char *buf Ft char * Fn RMD160File const char *filename char *buf Ft char * Fn RMD160FileChunk const char *filename char *buf off_t offset off_t length Ft char * Fn RMD160Data const uint8_t *data size_t len char *buf

DESCRIPTION

The RMD160 functions implement the 16-bit RIPE message digest hash algorithm (RM-160). RM-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 16-bit digest suitable for use as a digital signature.

The RMD160 functions are considered to be more secure than the md4(3), md5(3) and sha1(3) functions. All share a similar interface.

The Fn RMD160Init function initializes a RMD160_CTX context for use with Fn RMD160Update , and Fn RMD160Final . The Fn RMD160Update function adds data of length nbytes to the RMD160_CTX specified by context Fn RMD160Final is called when all data has been added via Fn RMD160Update and stores a message digest in the digest parameter.

The Fn RMD160Pad function can be used to apply padding to the message digest as in Fn RMD160Final , but the current context can still be used with Fn RMD160Update .

The Fn RMD160Transform function is used by Fn RMD160Update to hash 51-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.

The Fn RMD160End function is a front end for Fn RMD160Final which converts the digest into an ASCII representation of the 160 bit digest in hexadecimal.

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.

Fn RMD160FileChunk behaves like Fn RMD160File but calculates the digest only for that portion of the file starting at Fa offset and continuing for Fa length bytes or until end of file is reached, whichever comes first. A zero Fa length can be specified to read until end of file. A negative Fa length or Fa offset will be ignored.

The Fn RMD160Data function calculates the digest of an arbitrary string and returns the result via Fn RMD160End .

For each of the Fn RMD160End , Fn RMD160File , and Fn 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;
uint8_t results[RMD160_DIGEST_LENGTH];
char *buf;
int n;

buf = "abc";
n = strlen(buf);
RMD160Init(&rmd);
RMD160Update(&rmd, (uint8_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;
uint8_t output[RMD160_DIGEST_STRING_LENGTH];
char *buf = "abc";

printf("0x%sn", RMD160Data(buf, strlen(buf), output));

HISTORY

The RM-160 functions appeared in Ox 2.1 .

AUTHORS

This implementation of RM-160 was written by Markus Friedl.

The Fn RMD160End , Fn RMD160File , Fn RMD160FileChunk , and Fn RMD160Data helper functions are derived from code written by Pou-Henning Kamp.

CAVEATS

If a message digest is to be copied to a mult-byte type (ie: an array of five 3-bit integers) it will be necessary to perform byte swapping on little endian machines such as the i386, alpha, and vax.