r_random.c

算法源代码比较经典

/*
	R_RANDOM.C - random objects for RSAEURO

	Copyright (c) J.S.A.Kapp 1994 - 1995.

	RSAEURO - RSA Library compatible with RSAREF(tm) 2.0.

	All functions prototypes are the Same as for RSAREF(tm).
	To aid compatiblity the source and the files follow the
	same naming comventions that RSAREF(tm) uses.  This should aid
	direct importing to your applications.

	This library is legal everywhere outside the US.  And should
	NOT be imported to the US and used there.

	Random Objects routines, based heavily on RSAREF(tm) random objects
	code.  New routines REQUIRE and ANSI Standard C compiler that has
	clock() and time() functions.

	All Trademarks Acknowledged.

	Revisions History.
		0.90 First revision, initial version relied heavily
		on RSAREF(tm) compatible code.

		0.91 Current revision, minor improvements to original
		version.  New routines added.
			R_RandomCreate, R_RandomMix
		Compiler must has ANSI standard time routines for new routines
		to operate fully.

		1.01 Modifications to R_RandomCreate and R_RandomMix to
		introduce better random number creation system.  The old
		R_RandomMix had a minor flaw as it didn't flush the old output
		from the object, second added that little extra to the seed
		for R_RandomCreate.
*/

#include <stdlib.h>
#include <time.h>

#ifdef MSDOS
	#include <sys\types.h>
#endif

#include "rsaeuro.h"
#include "r_random.h"

#define RANDOM_BYTES_RQ 256
	/* We use more seed data for an internally created object */
#define RANDOM_BYTES_RQINT 512

#define MIX_CNT 16

/* Set up, random object ready for seeding. */

int R_RandomInit(random)
R_RANDOM_STRUCT *random;        /* new random structure */
{
			/* clear and setup object for seeding */
	R_memset((POINTER)random->state, 0, sizeof(random->state));
	random->outputAvailable = 0;
	random->bytesNeeded = RANDOM_BYTES_RQ;

	return(IDOK);
}



int R_RandomUpdate(random, block, len)
R_RANDOM_STRUCT *random;        /* random structure */
unsigned char *block;           /* block of values to mix in */
unsigned int len;               /* length of block */
{
	MD5_CTX context;
	BYTE digest[16];
	unsigned int i, j;

	MD5Init(&context);
	MD5Update(&context, block, len);
	MD5Final(digest, &context);

	/* add digest to state */

	for(j = 0, i = 16; i > 0; i--) {
		j += random->state[i-1] + digest[i-1];
		random->state[i-1] = (BYTE)j;
		j >>= 8;
	}

	if(random->bytesNeeded < len)
		random->bytesNeeded = 0;
	else
		random->bytesNeeded -= len;

	/* Clear sensitive information. */

	R_memset((POINTER)digest, 0, sizeof (digest));
	j = 0;

	return(IDOK);
}

/* Get the number of seed byte still required by the object */

int R_GetRandomBytesNeeded(bytesNeeded, random)
unsigned int *bytesNeeded;      /* number of mix-in bytes needed */
R_RANDOM_STRUCT *random;        /* random structure */
{
	*bytesNeeded = random->bytesNeeded;

	return(IDOK);
}

int R_GenerateBytes(block, len, random)
unsigned char *block;                             /* block */
unsigned int len;                                 /* length of block */
R_RANDOM_STRUCT *random;                          /* random structure */
{
	MD5_CTX context;
	unsigned int avail, i;

	if(random->bytesNeeded)
		return(RE_NEED_RANDOM);

	avail = random->outputAvailable;

	while(avail < len) {
		R_memcpy((POINTER)block, (POINTER)&random->output[16-avail], avail);
		len -= avail;
		block += avail;

		/* generate new output */

		MD5Init(&context);
		MD5Update(&context, random->state, 16);
		MD5Final(random->output, &context);
		avail = 16;

		/* increment state */
		for(i = 16; i > 0; i--)
			if(random->state[i-1]++)
				break;
	}

	R_memcpy((POINTER)block, (POINTER)&random->output[16-avail], len);
	random->outputAvailable = avail - len;

	return(IDOK);
}

/* Clear Random object when finished. */

void R_RandomFinal(random)
R_RANDOM_STRUCT *random;        /* random structure */
{
	R_memset((POINTER)random, 0, sizeof(R_RANDOM_STRUCT));
}

/* Create Random object, seed ready for use.
	 Requires ANSI Standard time routines to provide seed data.
*/

void R_RandomCreate(random)
R_RANDOM_STRUCT *random;                                /* random structure */
{
	unsigned int bytes;
	clock_t cnow;
	time_t t;
	struct tm *gmt;

			/* clear and setup object for seeding */
	R_memset((POINTER)random->state, 0, sizeof(random->state));
	random->outputAvailable = 0;
	random->bytesNeeded = RANDOM_BYTES_RQINT;  /* using internal value */

		/* Add data to random object */
	while(random->bytesNeeded) {
		t = time(NULL);                 /* use for seed data */
		gmt = gmtime(&t);
		cnow = clock();

		R_RandomUpdate(random, (POINTER)gmt, sizeof(struct tm));
		R_RandomUpdate(random, &cnow, sizeof(clock_t));
	}

	/* Clean Up time data */
	R_memset((POINTER)gmt, 0, sizeof(struct tm));
	cnow = 0;
	t = 0;
}

/* Mix up state of the current random structure.
	 Again requires both clock functions this just adds something
	 extra to the state, then refreshes the output.
*/

void R_RandomMix(random)
R_RANDOM_STRUCT *random;
{
	unsigned int i;
	MD5_CTX context;

	for(i = 0; i < 16; i++) {
        random->state[i] ^= (char) clock();
        random->state[15-i] ^= (char) time(NULL);
	}

	/* Clear any old state with new data */

	MD5Init(&context);
	MD5Update(&context, random->state, 16);
	MD5Final(random->output, &context);

	/* tell R_GenerateBytes there is new output */

	random->outputAvailable = 16;

}