ntru_ascii_poly.c

Go to the documentation of this file.

/*
 * 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_common.h"
#include "ntru_mem.h"
#include "ntru_params.h"
#include "ntru_poly.h"
#include "ntru_string.h"

#include <glib.h>

#include <stdint.h>
#include <stdlib.h>
#include <string.h>

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


static char *
get_int_to_bin_str(uint8_t value);


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

static char *
get_int_to_bin_str(uint8_t value)
{
    int i;
    const size_t bin_string_size = ASCII_BITS + 1;
    char *bin_string = ntru_malloc(sizeof(*bin_string) *
            (bin_string_size)); /* account for trailing null-byte */

    /* terminate properly */
    bin_string[bin_string_size - 1] = '\0';

    for (i = ASCII_BITS - 1; i >= 0; --i, value >>= 1)
        bin_string[i] = (value & 1) + '0';

    return bin_string;
}

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

fmpz_poly_t *
ascii_bin_to_bin_poly(const char *to_poly, const ntru_params *params)
{
    uint32_t i = 0;
    fmpz_poly_t *new_poly = ntru_malloc(sizeof(*new_poly));

    fmpz_poly_init(*new_poly);

    while (to_poly[i] && i < params->N) {
        fmpz_poly_set_coeff_si(*new_poly,
                i,
                (to_poly[i] == '0') ? -1 : 1);
        i++;
    }

    return new_poly;
}

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

fmpz_poly_t **
ascii_to_bin_poly_arr(const string *to_poly, const ntru_params *params)
{
    char *cur = to_poly->ptr;
    char *out = ntru_malloc(CHAR_SIZE * (to_poly->len * ASCII_BITS + 1));
    uint32_t polyc = 0;
    size_t out_len = 0;
    fmpz_poly_t **poly_array;

    for (uint32_t i = 0; i < to_poly->len; i++) {
        char *tmp_string = get_int_to_bin_str((int)(*cur));
        memcpy(out + out_len, tmp_string, ASCII_BITS);
        out_len += ASCII_BITS;
        cur++;
        free(tmp_string);
    }
    out[out_len] = '\0';

    poly_array = ntru_malloc(sizeof(**poly_array) *
            (strlen(out) / params->N + 1));

    for (uint32_t i = 0; i < out_len; i += params->N) {
        char chunk[params->N + 1];
        size_t real_chunk_size;

        real_chunk_size =
            (out_len - i > params->N) ? params->N : out_len - i;

        memcpy(chunk, out + i, real_chunk_size);
        chunk[real_chunk_size] = '\0';

        poly_array[polyc] = ascii_bin_to_bin_poly(chunk, params);

        polyc++;
    }

    free(out);

    poly_array[polyc] = NULL;

    return poly_array;
}

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

fmpz_poly_t **
base64_to_poly_arr(const string *to_poly, const ntru_params *params)
{
    uint32_t i = 0,
             polyc = 0;
    gsize out_len;
    guchar *base64_decoded = NULL,
           *base_tmp = NULL;
    string *new_string = ntru_malloc(sizeof(*new_string));
    fmpz_poly_t **poly_array;
    char *tmp = ntru_malloc(sizeof(char) * (to_poly->len + 1));

    /* g_base64_decode() needs it null-terminated */
    memcpy(tmp, to_poly->ptr, to_poly->len);
    tmp[to_poly->len] = '\0';

    base_tmp = g_base64_decode((const gchar *)tmp, &out_len);

    /* g_base64_decode() needs it null-terminated */
    REALLOC(tmp, sizeof(char) * (out_len + 1));
    memcpy(tmp, base_tmp, out_len);
    tmp[out_len] = '\0';

    base64_decoded = g_base64_decode((const gchar *)tmp, &out_len);

    new_string->ptr = (char *)base64_decoded;
    new_string->len = (unsigned long)(out_len);

    poly_array = ntru_malloc(sizeof(**poly_array) *
            (new_string->len / params->N));

    while (i < new_string->len) {
        uint32_t j = 0;
        fmpz_poly_t *new_poly = ntru_malloc(sizeof(*new_poly));

        fmpz_poly_init(*new_poly);

        while (j < params->N) {
            fmpz_poly_set_coeff_si(*new_poly,
                    j,
                    (uint8_t)(base64_decoded[i]));
            j++;
            i++;
        }

        /* fill the last poly with q (which is a non-standard
         * coefficient) */
        for (uint32_t k = j; k < params->N; k++) {
            fmpz_poly_set_coeff_si(*new_poly,
                    k,
                    params->q);
        }

        poly_array[polyc] = new_poly;
        polyc++;
    }

    poly_array[polyc] = NULL;

    string_delete(new_string);
    free(base_tmp);
    free(tmp);

    return poly_array;
}