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/*
* Copyright (C) 2013 Andreas Steffen
* HSR Hochschule fuer Technik Rapperswil
*
* This program is free software; you can redistribute it and/or modify it
* under the terms of the GNU General Public License as published by the
* Free Software Foundation; either version 2 of the License, or (at your
* option) any later version. See <http://www.fsf.org/copyleft/gpl.txt>.
*
* This program 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 General Public License
* for more details.
*/
#include "ntru_trits.h"
#include "ntru_mgf1.h"
#include "ntru_convert.h"
#include <utils/debug.h>
#include <utils/test.h>
typedef struct private_ntru_trits_t private_ntru_trits_t;
/**
* Private data of an ntru_trits_t object.
*/
struct private_ntru_trits_t {
/**
* Public ntru_trits_t interface.
*/
ntru_trits_t public;
/**
* Size of the trits array
*/
size_t trits_len;
/**
* Array containing a trit per octet
*/
uint8_t *trits;
};
METHOD(ntru_trits_t, get_size, size_t,
private_ntru_trits_t *this)
{
return this->trits_len;
}
METHOD(ntru_trits_t, get_trits, uint8_t*,
private_ntru_trits_t *this)
{
return this->trits;
}
METHOD(ntru_trits_t, destroy, void,
private_ntru_trits_t *this)
{
memwipe(this->trits, this->trits_len);
free(this->trits);
free(this);
}
/*
* Described in header.
*/
ntru_trits_t *ntru_trits_create(size_t len, hash_algorithm_t alg, chunk_t seed)
{
private_ntru_trits_t *this;
uint8_t octets[HASH_SIZE_SHA512], buf[5], *trits;
size_t hash_len, octet_count = 0, trits_needed, i;
ntru_mgf1_t *mgf1;
DBG2(DBG_LIB, "MGF1 is seeded with %u bytes", seed.len);
mgf1 = ntru_mgf1_create(alg, seed, TRUE);
if (!mgf1)
{
return NULL;
}
i = hash_len = mgf1->get_hash_size(mgf1);
INIT(this,
.public = {
.get_size = _get_size,
.get_trits = _get_trits,
.destroy = _destroy,
},
.trits_len = len,
.trits = malloc(len),
);
trits = this->trits;
trits_needed = this->trits_len;
while (trits_needed > 0)
{
if (i == hash_len)
{
/* get another block from MGF1 */
if (!mgf1->get_mask(mgf1, hash_len, octets))
{
mgf1->destroy(mgf1);
destroy(this);
return NULL;
}
octet_count += hash_len;
i = 0;
}
if (octets[i] < 243) /* 243 = 3^5 */
{
ntru_octet_2_trits(octets[i], (trits_needed < 5) ? buf : trits);
if (trits_needed < 5)
{
memcpy(trits, buf, trits_needed);
break;
}
trits += 5;
trits_needed -= 5;
}
i++;
}
DBG2(DBG_LIB, "MGF1 generates %u octets to extract %u trits",
octet_count, len);
mgf1->destroy(mgf1);
return &this->public;
}
EXPORT_FUNCTION_FOR_TESTS(ntru, ntru_trits_create);
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