md5lib is a set of routines that let you generate md5 digital signatures for various things. It's set up somewhat like stdio -- you open a md5 connection, write data to it, then close it and are handed back a signature.

JH md5_init()

Set up for generating a md5 signature. If md5_init() succeeds, it returns a JH handle which you then use when generating the signature.

void md5_put(bfr, count, handle)

Add the signature for the bfr into the current md5 signature.

char* md5_finish(handle, sig)

Finish building the digital signature for the current handle. If the caller passes in a signature buffer, the signature will be written into that buffer and a pointer to it will be returned, otherwise md5_finish will use a local static array for the signature.

To generate a digital signature for whatever's on stdin:

/*
 * compile with cc -o md5 md5.c -lbasis
 */
#include <stdio.h>
#include <md5lib.h>

main()
{
    JH handle;
    char bfr[512];
    unsigned char *sig;
    int siz, ix;

    if ((handle = md5_init()) == 0) {
	perror("md5_init");
	exit(1);
    }

    while ((siz = read(fileno(0), bfr, sizeof bfr)) > 0)
	md5_put(bfr, siz, handle);

    sig = md5_finish(handle, 0);

    for (ix = 0; ix < 16; ix++)
	printf("%02x", sig[ix]);
    putchar('\n');
}

There is a woeful lack of error checking. If you pass a bogus JH into md5_put or md5_finish, the function will most crash your program.

md5lib will silently return incorrect signatures for objects larger than 2^29 bytes (approximately 550 megabytes.)

None. This code is in the public domain, and you may do with it as you wish.

This code is written from the specification in RFC1321; it does not include code from the sample implementation there, or from any other source.

JH stands for John Hancock

orc@pell.chi.il.us (David Parsons).