104 lines
2.4 KiB
C
104 lines
2.4 KiB
C
/*
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* Copyright (C) 2014 FH Bielefeld
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*
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* This file is part of a FH Bielefeld project.
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*
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* This library is free software; you can redistribute it and/or
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* modify it under the terms of the GNU Lesser General Public
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* License as published by the Free Software Foundation; either
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* version 2.1 of the License, or (at your option) any later version.
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*
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* This library is distributed in the hope that it will be useful,
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* but WITHOUT ANY WARRANTY; without even the implied warranty of
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* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
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* Lesser General Public License for more details.
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*
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* You should have received a copy of the GNU Lesser General Public
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* License along with this library; if not, write to the Free Software
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* Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston,
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* MA 02110-1301 USA
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*/
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#include "context.h"
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#include "err.h"
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#include "rand.h"
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#include "poly.h"
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#include <stdio.h>
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#include <stdlib.h>
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#include <tompoly.h>
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#include <tommath.h>
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#include <sys/types.h>
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#include <sys/stat.h>
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#include <fcntl.h>
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#include <unistd.h>
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/*
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* static declarations
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*/
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static mp_digit get_urnd_int_small(int *sign);
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/**
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* Gets randomly a small integer
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* from the set {-1, 0, 1} using /dev/urandom.
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*
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* @param sign stores the signness [out]
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* @return random small integer
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*/
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static mp_digit get_urnd_int_small(int *sign)
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{
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int random_data;
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mp_digit random_int;
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ssize_t result;
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random_data = open("/dev/urandom", O_RDONLY);
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if ((result = read(random_data, &random_int, sizeof(random_int))) < 0)
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NTRU_ABORT("Unable to read /dev/urandom");
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close(random_data);
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if ((random_int % 2) == 0) {
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random_int = 0;
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*sign = 0;
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} else if (random_int % 3) {
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random_int = 1;
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*sign = 1;
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} else {
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random_int = 1;
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*sign = 0;
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}
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return random_int;
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}
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/**
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* Gets a random polynomial with coefficients
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* from the set {-1 ,0 ,1} using /dev/urandom.
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*
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* @param ctx the NTRU context
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* @return newly allocated polynomial
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*/
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pb_poly *ntru_get_urnd_poly_small(ntru_context *ctx)
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{
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mp_int chara;
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init_integer(&chara);
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pb_poly *poly = malloc(sizeof(pb_poly));
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init_polynom_size(poly, &chara, ctx->N);
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mp_clear(&chara);
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for (int i = 0; i < ctx->N; i++) {
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int sign;
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int c = get_urnd_int_small(&sign);
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mp_set(&(poly->terms[i]), (mp_digit)c);
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if (sign == 1)
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poly->terms[i].sign = 1;
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}
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poly->used = ctx->N;
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pb_clamp(poly);
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return poly;
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}
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