Tribblix: manual page: md4.3ext

MD4(3EXT) Extended Library Functions MD4(3EXT)

NAME

md4, MD4Init, MD4Update, MD4Final - MD4 digest functions

SYNOPSIS

cc [ flag ... ] file ... -lmd [ library ... ]
#include <md4.h>

void MD4Init(MD4_CTX *context);

void MD4Update(MD4_CTX *context, unsigned char *input,
size_t inlen);

void MD4Final(unsigned char *output, MD4_CTX *context);

DESCRIPTION

The MD4 functions implement the MD4 message-digest algorithm. The
algorithm takes as input a message of arbitrary length and produces a
"fingerprint" or "message digest" as output. The MD4 message-digest
algorithm is intended for digital signature applications in which
large files are "compressed" in a secure manner before being
encrypted with a private (secret) key under a public-key cryptosystem
such as RSA.

MD4Init(), MD4Update(), MD4Final()
The MD4Init(), MD4Update(), and MD4Final() functions allow an MD4
digest to be computed over multiple message blocks. Between blocks,
the state of the MD4 computation is held in an MD4 context structure
allocated by the caller. A complete digest computation consists of
calls to MD4 functions in the following order: one call to MD4Init(),
one or more calls to MD4Update(), and one call to MD4Final().

The MD4Init() function initializes the MD4 context structure pointed
to by context.

The MD4Update() function computes a partial MD4 digest on the
inlen-byte message block pointed to by input, and updates the MD4
context structure pointed to by context accordingly.

The MD4Final() function generates the final MD4 digest, using the MD4
context structure pointed to by context. The MD4 digest is written to
output. After a call to MD4Final(), the state of the context
structure is undefined. It must be reinitialized with MD4Init()
before it can be used again.

RETURN VALUES

These functions do not return a value.

SECURITY

The MD4 digest algorithm is not currently considered
cryptographically secure. It is included in libmd(3LIB) for use by
legacy protocols and systems only. It should not be used by new
systems or protocols.

EXAMPLES

Example 1: Authenticate a message found in multiple buffers

The following is a sample function that must authenticate a message
that is found in multiple buffers. The calling function provides an
authentication buffer that will contain the result of the MD4 digest.

#include <sys/types.h>
#include <sys/uio.h>
#include <md4.h>

int
AuthenticateMsg(unsigned char *auth_buffer, struct iovec
*messageIov, size_t num_buffers)
{
MD4_CTX ctx;
size_t i;

MD4Init(&ctx);

for(i=0; i<num_buffers; i++)
{
MD4Update(&ctx, messageIov->iov_base,
messageIov->iov_len);
messageIov += sizeof(struct iovec);
}

MD4Final(auth_buffer, &ctx);

return 0;
}

ATTRIBUTES