pqc/src/ascii_poly.c

126 lines
3.4 KiB
C

/*
* 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 "context.h"
#include "err.h"
#include "mem.h"
#include "poly.h"
#include "ascii_poly.h"
#include <math.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <sys/types.h>
#include <tommath.h>
#include <tompoly.h>
#define ASCII_DIGITS 7
/**
* Converts a string into a pb_poly of the size strlen(to_poly) * 7.
* 7 bit per ASCII symbol.
*
* @param to_poly the string
* @return the newly allocated polynom.
*/
pb_poly *ascii_to_poly(char *to_poly)
{
size_t length = (strlen(to_poly) * ASCII_DIGITS);
char *tmp_ptr = to_poly;
u_int8_t binary_Number[ASCII_DIGITS + 1];
if (!to_poly) {
return NULL;
}
mp_int chara;
init_integer(&chara);
pb_poly *poly = ntru_malloc(sizeof(pb_poly));
init_polynom_size(poly, &chara, length);
/* for every char */
for (u_int32_t j = 0; j < strlen(to_poly); j++) {
u_int8_t quotient = (u_int8_t) *tmp_ptr++;
u_int8_t k = ASCII_DIGITS;
for (u_int8_t i = 1; i <= ASCII_DIGITS; i++) {
/* gets the least significant bit in an array*/
binary_Number[k--] = quotient % 2;
/* bitshift so the next bit becomes the lsb*/
quotient >>= 1;
}
for (u_int8_t i = 1; i <= ASCII_DIGITS; i++) {
/* the actual position of the bit in the polynom */
u_int32_t coefficient = (i - 1) + (j * ASCII_DIGITS);
MP_SET(&(poly->terms[coefficient]), binary_Number[i]);
/* set the array to 0 so the next run is garbage free */
binary_Number[i] = 0;
poly->terms[i].sign = 0;
}
}
poly->used = (int) length;
mp_clear(&chara);
return poly;
}
/**
* Converts a polynom into a newly allocated string.
*
* @param to_ascii the polynom you want to make a string of.
* @return a pointer to the string ore a NULL pointer in the error case
*/
char *polynom_to_ascii(pb_poly *to_ascii)
{
if (!to_ascii) {
return NULL;
}
size_t length_poly = (size_t) to_ascii->used;
size_t length_string = (size_t) (length_poly / ASCII_DIGITS);
char *string = (char*) ntru_malloc(length_string);
char bit_buffer;
char *tmp_ptr = string;
u_int8_t ascii_value = 0;
/* every char */
for (u_int32_t i = 0; i < length_poly; i += ASCII_DIGITS) {
/* every bit*/
for (u_int32_t j = 0; j < ASCII_DIGITS; j++) {
/* get the bit */
if (mp_toradix(&(to_ascii->terms[i + j]), &bit_buffer, 2)) {
return NULL;
}
/* bit as integer */
u_int8_t bit = atoi(&bit_buffer);
/* bitshift to the left */
ascii_value <<= 1;
/* set the new bit and keep the other */
ascii_value |= bit;
}
/* char into string */
*tmp_ptr++ = (char) ascii_value;
/* reset for next char */
ascii_value = 0;
}
return string;
}