www.pudn.com > RSA-MD2-MD5-source_code.rar > prime.c, change:1994-03-26,size:3522b

```/* PRIME.C - primality-testing routines
*/

/* Copyright (C) RSA Laboratories, a division of RSA Data Security,
*/

#include "global.h"
#include "rsaref.h"
#include "r_random.h"
#include "nn.h"
#include "prime.h"

static unsigned int SMALL_PRIMES[] = { 3, 5, 7, 11 };
#define SMALL_PRIME_COUNT 4

static int ProbablePrime PROTO_LIST ((NN_DIGIT *, unsigned int));
static int SmallFactor PROTO_LIST ((NN_DIGIT *, unsigned int));
static int FermatTest PROTO_LIST ((NN_DIGIT *, unsigned int));

/* Generates a probable prime a between b and c such that a-1 is
divisible by d.

Lengths: a[digits], b[digits], c[digits], d[digits].
Assumes b < c, digits < MAX_NN_DIGITS.

Returns RE_NEED_RANDOM if randomStruct not seeded, RE_DATA if
unsuccessful.
*/
int GeneratePrime (a, b, c, d, digits, randomStruct)
NN_DIGIT *a, *b, *c, *d;
unsigned int digits;
R_RANDOM_STRUCT *randomStruct;
{
int status;
unsigned char block[MAX_NN_DIGITS * NN_DIGIT_LEN];
NN_DIGIT t[MAX_NN_DIGITS], u[MAX_NN_DIGITS];

/* Generate random number between b and c.
*/
if (status = R_GenerateBytes (block, digits * NN_DIGIT_LEN, randomStruct))
return (status);
NN_Decode (a, digits, block, digits * NN_DIGIT_LEN);
NN_Sub (t, c, b, digits);
NN_ASSIGN_DIGIT (u, 1, digits);
NN_Mod (a, a, digits, t, digits);

/* Adjust so that a-1 is divisible by d.
*/
NN_Mod (t, a, digits, d, digits);
NN_Sub (a, a, t, digits);
if (NN_Cmp (a, b, digits) < 0)
if (NN_Cmp (a, c, digits) > 0)
NN_Sub (a, a, d, digits);

/* Search to c in steps of d.
*/
NN_Assign (t, c, digits);
NN_Sub (t, t, d, digits);

while (! ProbablePrime (a, digits)) {
if (NN_Cmp (a, t, digits) > 0)
return (RE_DATA);
}

return (0);
}

/* Returns nonzero iff a is a probable prime.

*/
NN_DIGIT *a;
{
}

/* Returns nonzero iff a has a prime factor in SMALL_PRIMES.

*/
NN_DIGIT *a;
{
int status;
NN_DIGIT t[1];
unsigned int i;

status = 0;

for (i = 0; i < SMALL_PRIME_COUNT; i++) {
NN_ASSIGN_DIGIT (t, SMALL_PRIMES[i], 1);
if ((aDigits == 1) && ! NN_Cmp (a, t, 1))
break;
NN_Mod (t, a, aDigits, t, 1);
if (NN_Zero (t, 1)) {
status = 1;
break;
}
}

/* Zeroize sensitive information.
*/
i = 0;
R_memset ((POINTER)t, 0, sizeof (t));

return (status);
}

/* Returns nonzero iff a passes Fermat's test for witness 2.
(All primes pass the test, and nearly all composites fail.)

*/
NN_DIGIT *a;
{
int status;
NN_DIGIT t[MAX_NN_DIGITS], u[MAX_NN_DIGITS];