bn_modfs.c is no longer needed, a BN_sqrt implementation

/*

 *

 *	bn_modfs.c

 *

 *	Some Modular Arithmetic Functions.

 *

 *	Copyright (C) Lenka Fibikova 2000

 *

 *

 */

#include <stdio.h>

#include <stdlib.h>

#include <assert.h>

#include "bn_modfs.h"

#define MAX_ROUNDS	10

int BN_mod_sqrt(BIGNUM *x, BIGNUM *a, BIGNUM *p, BN_CTX *ctx) 

/* x^2 = a (mod p) */

	{

	int ret;

	BIGNUM *n0, *n1, *r, *b, *m;

	int max;

	assert(x != NULL && a != NULL && p != NULL && ctx != NULL);

	assert(BN_cmp(a, p) < 0);

	ret = BN_kronecker(a, p, ctx);

	if (ret < 0 || ret > 1) return 0;

	if (ret == 0)

		{

		if (!BN_zero(x)) return 0;

		return 1;

		}

	BN_CTX_start(ctx);

	n0 = BN_CTX_get(ctx);

	n1 = BN_CTX_get(ctx);

	if (n1 == NULL) goto err;

	if ((r = BN_new()) == NULL) goto err;

	if ((b = BN_new()) == NULL) goto err;

	if ((m = BN_new()) == NULL) goto err;

	if (!BN_zero(n0)) goto err;

	if (!BN_zero(n1)) goto err;

	if (!BN_zero(r)) goto err;

	if (!BN_zero(b)) goto err;

	if (!BN_zero(m)) goto err;

	max = 0;

	do

		{

		if (max++ > MAX_ROUNDS) goto err; /* if p is not prime could never stop*/

		if (!BN_add_word(m, 1)) goto err;

		ret = BN_kronecker(m, p, ctx);

		if (ret < -1 || ret > 1) goto err;

		}

	while (ret != -1);

	if (BN_copy(n1, p) == NULL) goto err;

	if (!BN_sub_word(n1, 1)) goto err;

	while (!BN_is_odd(n1))

		{

		if (!BN_add_word(r, 1)) goto err;

		if (!BN_rshift1(n1, n1)) goto err;

		}

	if (!BN_mod_exp_simple(n0, m, n1, p, ctx)) goto err;

	if (!BN_sub_word(n1, 1)) goto err;

	if (!BN_rshift1(n1, n1)) goto err;

	if (!BN_mod_exp_simple(x, a, n1, p, ctx)) goto err;

	if (!BN_mod_sqr(b, x, p, ctx)) goto err;

	if (!BN_mod_mul(b, b, a, p, ctx)) goto err;

	if (!BN_mod_mul(x, x, a, p, ctx)) goto err;

	while (!BN_is_one(b))

		{

		if (!BN_one(m)) goto err;

		if (!BN_mod_sqr(n1, b, p, ctx)) goto err;

		while(!BN_is_one(n1))

			{

			if (!BN_mod_mul(n1, n1, n1, p, ctx)) goto err;

			if (!BN_add_word(m, 1)) goto err;

			}

		if (!BN_sub(r, r, m)) goto err;

		if (!BN_sub_word(r, 1)) goto err;

		if (r->neg) goto err;

		if (BN_copy(n1, n0) == NULL) goto err;

		while(!BN_is_zero(r))

			{

			if (!BN_mod_mul(n1, n1, n1, p, ctx)) goto err;

			if (!BN_sub_word(r, 1)) goto err;

			}

		if (!BN_mod_mul(n0, n1, n1, p, ctx)) goto err;

		if (BN_copy(r, m) == NULL) goto err;

		if (!BN_mod_mul(x, x, n1, p, ctx)) goto err;

		if (!BN_mod_mul(b, b, n0, p, ctx)) goto err;

		}

#ifdef TEST

	BN_mod_sqr(n0, x, p, ctx);

	if (BN_cmp(n0, a)) goto err;

#endif

	if (r != NULL) BN_clear_free(r);

	if (b != NULL) BN_clear_free(b);

	if (m != NULL) BN_clear_free(m);

	BN_CTX_end(ctx);

	return 1;

err:

	if (r != NULL) BN_clear_free(r);

	if (b != NULL) BN_clear_free(b);

	if (m != NULL) BN_clear_free(m);

	BN_CTX_end(ctx);

	return 0;

	}

/*

 *

 *	bn_modfs.h

 *

 *	Some Modular Arithmetic Functions.

 *

 *	Copyright (C) Lenka Fibikova 2000

 *

 *

 */

#ifndef HEADER_BN_MODFS_H

#define HEADER_BN_MODFS_H

#include <openssl/bn.h>

int BN_mod_sqrt(BIGNUM *x, BIGNUM *a, BIGNUM *p, BN_CTX *ctx);

#endif