ec_mult.c

OpenSSL 0.9.8k 最新版OpenSSL

		}

	if (numblocks)
		{
		/* we go here iff scalar != NULL */
		
		if (pre_comp == NULL)
			{
			if (num_scalar != 1)
				{
				ECerr(EC_F_EC_WNAF_MUL, ERR_R_INTERNAL_ERROR);
				goto err;
				}
			/* we have already generated a wNAF for 'scalar' */
			}
		else
			{
			signed char *tmp_wNAF = NULL;
			size_t tmp_len = 0;
			
			if (num_scalar != 0)
				{
				ECerr(EC_F_EC_WNAF_MUL, ERR_R_INTERNAL_ERROR);
				goto err;
				}

			/* use the window size for which we have precomputation */
			wsize[num] = pre_comp->w;
			tmp_wNAF = compute_wNAF(scalar, wsize[num], &tmp_len);
			if (!tmp_wNAF)
				goto err;

			if (tmp_len <= max_len)
				{
				/* One of the other wNAFs is at least as long
				 * as the wNAF belonging to the generator,
				 * so wNAF splitting will not buy us anything. */

				numblocks = 1;
				totalnum = num + 1; /* don't use wNAF splitting */
				wNAF[num] = tmp_wNAF;
				wNAF[num + 1] = NULL;
				wNAF_len[num] = tmp_len;
				if (tmp_len > max_len)
					max_len = tmp_len;
				/* pre_comp->points starts with the points that we need here: */
				val_sub[num] = pre_comp->points;
				}
			else
				{
				/* don't include tmp_wNAF directly into wNAF array
				 * - use wNAF splitting and include the blocks */

				signed char *pp;
				EC_POINT **tmp_points;
				
				if (tmp_len < numblocks * blocksize)
					{
					/* possibly we can do with fewer blocks than estimated */
					numblocks = (tmp_len + blocksize - 1) / blocksize;
					if (numblocks > pre_comp->numblocks)
						{
						ECerr(EC_F_EC_WNAF_MUL, ERR_R_INTERNAL_ERROR);
						goto err;
						}
					totalnum = num + numblocks;
					}
				
				/* split wNAF in 'numblocks' parts */
				pp = tmp_wNAF;
				tmp_points = pre_comp->points;

				for (i = num; i < totalnum; i++)
					{
					if (i < totalnum - 1)
						{
						wNAF_len[i] = blocksize;
						if (tmp_len < blocksize)
							{
							ECerr(EC_F_EC_WNAF_MUL, ERR_R_INTERNAL_ERROR);
							goto err;
							}
						tmp_len -= blocksize;
						}
					else
						/* last block gets whatever is left
						 * (this could be more or less than 'blocksize'!) */
						wNAF_len[i] = tmp_len;
					
					wNAF[i + 1] = NULL;
					wNAF[i] = OPENSSL_malloc(wNAF_len[i]);
					if (wNAF[i] == NULL)
						{
						ECerr(EC_F_EC_WNAF_MUL, ERR_R_MALLOC_FAILURE);
						OPENSSL_free(tmp_wNAF);
						goto err;
						}
					memcpy(wNAF[i], pp, wNAF_len[i]);
					if (wNAF_len[i] > max_len)
						max_len = wNAF_len[i];

					if (*tmp_points == NULL)
						{
						ECerr(EC_F_EC_WNAF_MUL, ERR_R_INTERNAL_ERROR);
						OPENSSL_free(tmp_wNAF);
						goto err;
						}
					val_sub[i] = tmp_points;
					tmp_points += pre_points_per_block;
					pp += blocksize;
					}
				OPENSSL_free(tmp_wNAF);
				}
			}
		}

	/* All points we precompute now go into a single array 'val'.
	 * 'val_sub[i]' is a pointer to the subarray for the i-th point,
	 * or to a subarray of 'pre_comp->points' if we already have precomputation. */
	val = OPENSSL_malloc((num_val + 1) * sizeof val[0]);
	if (val == NULL)
		{
		ECerr(EC_F_EC_WNAF_MUL, ERR_R_MALLOC_FAILURE);
		goto err;
		}
	val[num_val] = NULL; /* pivot element */

	/* allocate points for precomputation */
	v = val;
	for (i = 0; i < num + num_scalar; i++)
		{
		val_sub[i] = v;
		for (j = 0; j < (1u << (wsize[i] - 1)); j++)
			{
			*v = EC_POINT_new(group);
			if (*v == NULL) goto err;
			v++;
			}
		}
	if (!(v == val + num_val))
		{
		ECerr(EC_F_EC_WNAF_MUL, ERR_R_INTERNAL_ERROR);
		goto err;
		}

	if (!(tmp = EC_POINT_new(group)))
		goto err;

	/* prepare precomputed values:
	 *    val_sub[i][0] :=     points[i]
	 *    val_sub[i][1] := 3 * points[i]
	 *    val_sub[i][2] := 5 * points[i]
	 *    ...
	 */
	for (i = 0; i < num + num_scalar; i++)
		{
		if (i < num)
			{
			if (!EC_POINT_copy(val_sub[i][0], points[i])) goto err;
			}
		else
			{
			if (!EC_POINT_copy(val_sub[i][0], generator)) goto err;
			}

		if (wsize[i] > 1)
			{
			if (!EC_POINT_dbl(group, tmp, val_sub[i][0], ctx)) goto err;
			for (j = 1; j < (1u << (wsize[i] - 1)); j++)
				{
				if (!EC_POINT_add(group, val_sub[i][j], val_sub[i][j - 1], tmp, ctx)) goto err;
				}
			}
		}

#if 1 /* optional; EC_window_bits_for_scalar_size assumes we do this step */
	if (!EC_POINTs_make_affine(group, num_val, val, ctx))
		goto err;
#endif

	r_is_at_infinity = 1;

	for (k = max_len - 1; k >= 0; k--)
		{
		if (!r_is_at_infinity)
			{
			if (!EC_POINT_dbl(group, r, r, ctx)) goto err;
			}
		
		for (i = 0; i < totalnum; i++)
			{
			if (wNAF_len[i] > (size_t)k)
				{
				int digit = wNAF[i][k];
				int is_neg;

				if (digit) 
					{
					is_neg = digit < 0;

					if (is_neg)
						digit = -digit;

					if (is_neg != r_is_inverted)
						{
						if (!r_is_at_infinity)
							{
							if (!EC_POINT_invert(group, r, ctx)) goto err;
							}
						r_is_inverted = !r_is_inverted;
						}

					/* digit > 0 */

					if (r_is_at_infinity)
						{
						if (!EC_POINT_copy(r, val_sub[i][digit >> 1])) goto err;
						r_is_at_infinity = 0;
						}
					else
						{
						if (!EC_POINT_add(group, r, r, val_sub[i][digit >> 1], ctx)) goto err;
						}
					}
				}
			}
		}

	if (r_is_at_infinity)
		{
		if (!EC_POINT_set_to_infinity(group, r)) goto err;
		}
	else
		{
		if (r_is_inverted)
			if (!EC_POINT_invert(group, r, ctx)) goto err;
		}
	
	ret = 1;

 err:
	if (new_ctx != NULL)
		BN_CTX_free(new_ctx);
	if (tmp != NULL)
		EC_POINT_free(tmp);
	if (wsize != NULL)
		OPENSSL_free(wsize);
	if (wNAF_len != NULL)
		OPENSSL_free(wNAF_len);
	if (wNAF != NULL)
		{
		signed char **w;
		
		for (w = wNAF; *w != NULL; w++)
			OPENSSL_free(*w);
		
		OPENSSL_free(wNAF);
		}
	if (val != NULL)
		{
		for (v = val; *v != NULL; v++)
			EC_POINT_clear_free(*v);

		OPENSSL_free(val);
		}
	if (val_sub != NULL)
		{
		OPENSSL_free(val_sub);
		}
	return ret;
	}


/* ec_wNAF_precompute_mult()
 * creates an EC_PRE_COMP object with preprecomputed multiples of the generator
 * for use with wNAF splitting as implemented in ec_wNAF_mul().
 * 
 * 'pre_comp->points' is an array of multiples of the generator
 * of the following form:
 * points[0] =     generator;
 * points[1] = 3 * generator;
 * ...
 * points[2^(w-1)-1] =     (2^(w-1)-1) * generator;
 * points[2^(w-1)]   =     2^blocksize * generator;
 * points[2^(w-1)+1] = 3 * 2^blocksize * generator;
 * ...
 * points[2^(w-1)*(numblocks-1)-1] = (2^(w-1)) *  2^(blocksize*(numblocks-2)) * generator
 * points[2^(w-1)*(numblocks-1)]   =              2^(blocksize*(numblocks-1)) * generator
 * ...
 * points[2^(w-1)*numblocks-1]     = (2^(w-1)) *  2^(blocksize*(numblocks-1)) * generator
 * points[2^(w-1)*numblocks]       = NULL
 */
int ec_wNAF_precompute_mult(EC_GROUP *group, BN_CTX *ctx)
	{
	const EC_POINT *generator;
	EC_POINT *tmp_point = NULL, *base = NULL, **var;
	BN_CTX *new_ctx = NULL;
	BIGNUM *order;
	size_t i, bits, w, pre_points_per_block, blocksize, numblocks, num;
	EC_POINT **points = NULL;
	EC_PRE_COMP *pre_comp;
	int ret = 0;

	/* if there is an old EC_PRE_COMP object, throw it away */
	EC_EX_DATA_free_data(&group->extra_data, ec_pre_comp_dup, ec_pre_comp_free, ec_pre_comp_clear_free);

	if ((pre_comp = ec_pre_comp_new(group)) == NULL)
		return 0;

	generator = EC_GROUP_get0_generator(group);
	if (generator == NULL)
		{
		ECerr(EC_F_EC_WNAF_PRECOMPUTE_MULT, EC_R_UNDEFINED_GENERATOR);
		goto err;
		}

	if (ctx == NULL)
		{
		ctx = new_ctx = BN_CTX_new();
		if (ctx == NULL)
			goto err;
		}
	
	BN_CTX_start(ctx);
	order = BN_CTX_get(ctx);
	if (order == NULL) goto err;
	
	if (!EC_GROUP_get_order(group, order, ctx)) goto err;		
	if (BN_is_zero(order))
		{
		ECerr(EC_F_EC_WNAF_PRECOMPUTE_MULT, EC_R_UNKNOWN_ORDER);
		goto err;
		}

	bits = BN_num_bits(order);
	/* The following parameters mean we precompute (approximately)
	 * one point per bit.
	 *
	 * TBD: The combination  8, 4  is perfect for 160 bits; for other
	 * bit lengths, other parameter combinations might provide better
	 * efficiency.
	 */
	blocksize = 8;
	w = 4;
	if (EC_window_bits_for_scalar_size(bits) > w)
		{
		/* let's not make the window too small ... */
		w = EC_window_bits_for_scalar_size(bits);
		}

	numblocks = (bits + blocksize - 1) / blocksize; /* max. number of blocks to use for wNAF splitting */
	
	pre_points_per_block = 1u << (w - 1);
	num = pre_points_per_block * numblocks; /* number of points to compute and store */

	points = OPENSSL_malloc(sizeof (EC_POINT*)*(num + 1));
	if (!points)
		{
		ECerr(EC_F_EC_WNAF_PRECOMPUTE_MULT, ERR_R_MALLOC_FAILURE);
		goto err;
		}

	var = points;
	var[num] = NULL; /* pivot */
	for (i = 0; i < num; i++)
		{
		if ((var[i] = EC_POINT_new(group)) == NULL)
			{
			ECerr(EC_F_EC_WNAF_PRECOMPUTE_MULT, ERR_R_MALLOC_FAILURE);
			goto err;
			}
		}

	if (!(tmp_point = EC_POINT_new(group)) || !(base = EC_POINT_new(group)))
		{
		ECerr(EC_F_EC_WNAF_PRECOMPUTE_MULT, ERR_R_MALLOC_FAILURE);
		goto err;
		}	
	
	if (!EC_POINT_copy(base, generator))
		goto err;
	
	/* do the precomputation */
	for (i = 0; i < numblocks; i++)
		{
		size_t j;

		if (!EC_POINT_dbl(group, tmp_point, base, ctx))
			goto err;

		if (!EC_POINT_copy(*var++, base))
			goto err;

		for (j = 1; j < pre_points_per_block; j++, var++)
			{
			/* calculate odd multiples of the current base point */
			if (!EC_POINT_add(group, *var, tmp_point, *(var - 1), ctx))
				goto err;
			}

		if (i < numblocks - 1)
			{
			/* get the next base (multiply current one by 2^blocksize) */
			size_t k;

			if (blocksize <= 2)
				{
				ECerr(EC_F_EC_WNAF_PRECOMPUTE_MULT, ERR_R_INTERNAL_ERROR);
				goto err;
				}				

			if (!EC_POINT_dbl(group, base, tmp_point, ctx))
				goto err;
			for (k = 2; k < blocksize; k++)
				{
				if (!EC_POINT_dbl(group,base,base,ctx))
					goto err;
				}
			}
 		}

	if (!EC_POINTs_make_affine(group, num, points, ctx))
		goto err;
	
	pre_comp->group = group;
	pre_comp->blocksize = blocksize;
	pre_comp->numblocks = numblocks;
	pre_comp->w = w;
	pre_comp->points = points;
	points = NULL;
	pre_comp->num = num;

	if (!EC_EX_DATA_set_data(&group->extra_data, pre_comp,
		ec_pre_comp_dup, ec_pre_comp_free, ec_pre_comp_clear_free))
		goto err;
	pre_comp = NULL;

	ret = 1;
 err:
	if (ctx != NULL)
		BN_CTX_end(ctx);
	if (new_ctx != NULL)
		BN_CTX_free(new_ctx);
	if (pre_comp)
		ec_pre_comp_free(pre_comp);
	if (points)
		{
		EC_POINT **p;

		for (p = points; *p != NULL; p++)
			EC_POINT_free(*p);
		OPENSSL_free(points);
		}
	if (tmp_point)
		EC_POINT_free(tmp_point);
	if (base)
		EC_POINT_free(base);
	return ret;
	}


int ec_wNAF_have_precompute_mult(const EC_GROUP *group)
	{
	if (EC_EX_DATA_get_data(group->extra_data, ec_pre_comp_dup, ec_pre_comp_free, ec_pre_comp_clear_free) != NULL)
		return 1;
	else
		return 0;
	}