pqc/src/poly.c

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/*
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* Copyright (C) 2014 FH Bielefeld
*
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* 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 <stdbool.h>
#include <stdio.h>
#include <tompoly.h>
#include <tommath.h>
/**
* Initialize a mp_int and check if this was successful, the
* caller must free new_int with mp_clear().
*
* @param new_int a pointer to the mp_int you want to initialize
*/
void init_integer(mp_int *new_int)
{
int result;
if ((result = mp_init(new_int)) != MP_OKAY) {
NTRU_ABORT("Error initializing the number. %s",
mp_error_to_string(result));
}
}
/**
* Initialize a Polynom with a pb_poly and a mp_int as characteristic.
* Checks if everything went fine. The caller must free new_poly
* with pb_clear().
*
* @param new_poly the pb_poly you want to initialize
* @param chara the characteristic
*/
void init_polynom(pb_poly *new_poly, mp_int *chara)
{
int result;
if ((result = pb_init(new_poly, chara)) != MP_OKAY) {
NTRU_ABORT("Error initializing the number. %s",
mp_error_to_string(result));
}
}
/**
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* Initialize a Polynom with a pb_poly and an mp_int as characteristic
* with size. Checks if everything went fine. The caller must free
* new_poly with pb_clear().
*
* @param new_poly the pb_poly you want to initialize
* @param chara the characteristic
* @param size the size of the polynomial
*/
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void init_polynom_size(pb_poly *new_poly, mp_int *chara, size_t size)
{
int result;
if ((result = pb_init_size(new_poly, chara, size)) != MP_OKAY) {
NTRU_ABORT("Error initializing the number. %s",
mp_error_to_string(result));
}
}
/**
* Initializes and builds a polynomial with the
* coefficient values of c[] of size len within NTRU
* context ctx and returns a newly allocated polynomial
* pointer which is not clamped.
*
* If you want to fill a polyonmial of length 11 with zeros,
* call build_polynom(NULL, 11, ctx).
*
* @param c array of polynomial coefficients, can be NULL
* @param len size of the coefficient array, can be 0
* @param ctx NTRU context
* @return newly allocated polynomial pointer, must be freed
* with delete_polynom()
*/
pb_poly *build_polynom(int const * const c,
const size_t len,
ntru_context *ctx)
{
pb_poly *new_poly;
mp_int chara;
new_poly = malloc(sizeof(*new_poly));
init_integer(&chara);
init_polynom_size(new_poly, &chara, len);
mp_clear(&chara);
/* fill the polynom if c is not NULL */
if (c) {
for (unsigned int i = 0; i < len; i++) {
bool sign = false;
unsigned long unsigned_c;
if (c[i] < 0) {
unsigned_c = 0 - c[i];
sign = true;
} else {
unsigned_c = c[i];
}
mp_set_int(&(new_poly->terms[i]), unsigned_c);
if (sign == true)
new_poly->terms[i].sign = 1;
}
} else { /* fill with zeros */
for (unsigned int i = 0; i < len; i++)
mp_set(&(new_poly->terms[i]), 0);
}
new_poly->used = len;
return new_poly;
}
/**
* This deletes the internal structure of a polynomial,
* and frees the pointer. Don't call this on stack variables,
* this is intended for use after ntru_ functions, that
* return a polynomial pointer.
*
* @param poly the polynomial to delete
*/
void delete_polynom(pb_poly *poly)
{
pb_clear(poly);
free(poly);
}
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/**
* Starmultiplication, as follows:
* c = a * b mod x^(N 1)
*
* @param a polynom to multiply
* @param b polynom to multiply
* @param c polynom [out]
* @param ctx NTRU context
* @param modulus whether we use p or q
*/
void pb_starmultiply(pb_poly *a,
pb_poly *b,
pb_poly *c,
ntru_context *ctx,
unsigned int modulus)
{
for (int k = ctx->N - 1; k >= 0; k--) {
int j;
j = k + 1;
for (int i = ctx->N - 1; i >= 0; i--) {
if (j == (int)(ctx->N))
j = 0;
if (mp_cmp_d(&(a->terms[i]), (mp_digit)0) != MP_EQ &&
mp_cmp_d(&(b->terms[j]), (mp_digit)0) != MP_EQ) {
int result;
mp_int mp_modulus;
mp_int mp_tmp;
init_integer(&mp_tmp);
init_integer(&mp_modulus);
mp_set_int(&mp_modulus, (unsigned long)(modulus));
if ((result = mp_mul(&(a->terms[i]),
&(b->terms[j]), &mp_tmp)) != MP_OKAY)
NTRU_ABORT("Error multiplying terms. %s",
mp_error_to_string(result));
if ((result = mp_add(&(c->terms[k]),
&mp_tmp, &(c->terms[k]))) != MP_OKAY)
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NTRU_ABORT("Error adding terms. %s",
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mp_error_to_string(result));
if ((result = mp_mod(&(c->terms[k]),
&mp_modulus, &(c->terms[k]))) != MP_OKAY)
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NTRU_ABORT("Error redrucing term by modulo. %s",
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mp_error_to_string(result));
mp_clear(&mp_modulus);
mp_clear(&mp_tmp);
}
j++;
}
}
}
/**
* Print the polynomial in a human readable format to stdout.
*
* @param poly to draw
*/
void draw_polynom(pb_poly * const poly)
{
int x;
char buf[8192];
if (poly->used == 0) {
printf("0");
} else {
for (x = poly->used - 1; x >= 0; x--) {
if (mp_iszero(&(poly->terms[x])) == MP_YES)
continue;
mp_toradix(&(poly->terms[x]), buf, 10);
if ((x != poly->used - 1) && poly->terms[x].sign == MP_ZPOS) {
printf("+");
}
printf(" %sx^%d ", buf, x);
}
}
if (mp_iszero(&(poly->characteristic)) == MP_NO) {
mp_toradix(&(poly->characteristic), buf, 10);
printf(" (mod %s)", buf);
}
printf("\n");
}