ntru_encrypt.c

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/*
 * Copyright (C) 2014 FH Bielefeld
 *
 * This file is part of a FH Bielefeld project.
 *
 * This library is free software; you can redistribute it and/or
 * modify it under the terms of the GNU Lesser General Public
 * License as published by the Free Software Foundation; either
 * version 2.1 of the License, or (at your option) any later version.
 *
 * This library is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
 * Lesser General Public License for more details.
 *
 * You should have received a copy of the GNU Lesser General Public
 * License along with this library; if not, write to the Free Software
 * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston,
 * MA  02110-1301  USA
 */

#include "ntru_ascii_poly.h"
#include "ntru_encrypt.h"
#include "ntru_mem.h"
#include "ntru_params.h"
#include "ntru_poly.h"
#include "ntru_poly_ascii.h"
#include "ntru_string.h"

#include <string.h>

#include <fmpz_poly.h>
#include <fmpz.h>


/*------------------------------------------------------------------------*/

void
ntru_encrypt_poly(
        const fmpz_poly_t msg_bin,
        const fmpz_poly_t pub_key,
        const fmpz_poly_t rnd,
        fmpz_poly_t out,
        const ntru_params *params)
{
    fmpz_poly_t tmp_poly_msg;

    if (!msg_bin || !pub_key || !rnd || !out || !params)
        NTRU_ABORT_DEBUG("Unexpected NULL parameters");

    /* allow aliasing */
    fmpz_poly_init(tmp_poly_msg);
    fmpz_poly_set(tmp_poly_msg, msg_bin);

    fmpz_poly_zero(out);
    poly_starmultiply(pub_key, rnd, out, params, params->q);

    fmpz_poly_add(out, out, tmp_poly_msg);
    fmpz_poly_mod_unsigned(out, params->q);

    fmpz_poly_clear(tmp_poly_msg);
}

/*------------------------------------------------------------------------*/

string *
ntru_encrypt_string(
        const string *msg,
        const fmpz_poly_t pub_key,
        const fmpz_poly_t rnd,
        const ntru_params *params)
{
    uint32_t i = 0;
    string *enc_msg;
    fmpz_poly_t **poly_array;

    if (!msg || !msg->len)
        NTRU_ABORT_DEBUG("Unexpected NULL parameters");

    poly_array = ascii_to_bin_poly_arr(msg, params);

    while (*poly_array[i]) {
        ntru_encrypt_poly(*poly_array[i],
                pub_key,
                rnd,
                *poly_array[i],
                params);
        i++;
    }

    enc_msg = poly_arr_to_base64((const fmpz_poly_t **)poly_array,
            i, params);

    poly_delete_array(poly_array);

    return enc_msg;
}

/*------------------------------------------------------------------------*/