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ec_params.c
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/*
* Copyright (C) 2017 - This file is part of libecc project
*
* Authors:
* Ryad BENADJILA <ryadbenadjila@gmail.com>
* Arnaud EBALARD <arnaud.ebalard@ssi.gouv.fr>
* Jean-Pierre FLORI <jean-pierre.flori@ssi.gouv.fr>
*
* Contributors:
* Nicolas VIVET <nicolas.vivet@ssi.gouv.fr>
* Karim KHALFALLAH <karim.khalfallah@ssi.gouv.fr>
*
* This software is licensed under a dual BSD and GPL v2 license.
* See LICENSE file at the root folder of the project.
*/
#include "ec_params.h"
#include "curves.h"
/*
* Initialize (already allocated) curve parameters structure pointed by
* ec_params using value provided in remaining parameters.
*/
void import_params(ec_params *out_params, const ec_str_params *in_str_params)
{
nn tmp_p, tmp_p_bitlen, tmp_r, tmp_r_square, tmp_mpinv, tmp_p_shift;
nn tmp_p_normalized, tmp_p_reciprocal, tmp_curve_order, tmp_order;
nn tmp_order_bitlen, tmp_cofactor;
fp tmp_a, tmp_b, tmp_gx, tmp_gy, tmp_gz;
MUST_HAVE((out_params != NULL) && (in_str_params != NULL));
local_memset(out_params, 0, sizeof(ec_params));
/*
* We first need to import p, the prime defining Fp and associated
* Montgomery parameters (r, r^2 and mpinv)
*/
nn_init_from_buf(&tmp_p, PARAM_BUF_PTR(in_str_params->p),
PARAM_BUF_LEN(in_str_params->p));
nn_init_from_buf(&tmp_p_bitlen,
PARAM_BUF_PTR(in_str_params->p_bitlen),
PARAM_BUF_LEN(in_str_params->p_bitlen));
nn_init_from_buf(&tmp_r, PARAM_BUF_PTR(in_str_params->r),
PARAM_BUF_LEN(in_str_params->r));
nn_init_from_buf(&tmp_r_square,
PARAM_BUF_PTR(in_str_params->r_square),
PARAM_BUF_LEN(in_str_params->r_square));
nn_init_from_buf(&tmp_mpinv,
PARAM_BUF_PTR(in_str_params->mpinv),
PARAM_BUF_LEN(in_str_params->mpinv));
nn_init_from_buf(&tmp_p_shift,
PARAM_BUF_PTR(in_str_params->p_shift),
PARAM_BUF_LEN(in_str_params->p_shift));
nn_init_from_buf(&tmp_p_normalized,
PARAM_BUF_PTR(in_str_params->p_normalized),
PARAM_BUF_LEN(in_str_params->p_normalized));
nn_init_from_buf(&tmp_p_reciprocal,
PARAM_BUF_PTR(in_str_params->p_reciprocal),
PARAM_BUF_LEN(in_str_params->p_reciprocal));
/* From p, we can create global Fp context */
fp_ctx_init(&(out_params->ec_fp), &tmp_p,
(bitcnt_t)(tmp_p_bitlen.val[0]),
&tmp_r, &tmp_r_square,
tmp_mpinv.val[0], (bitcnt_t)tmp_p_shift.val[0],
&tmp_p_normalized, tmp_p_reciprocal.val[0]);
/*
* Having Fp context, we can import a and b, the coefficient of
* of Weierstrass equation.
*/
fp_init_from_buf(&tmp_a, &(out_params->ec_fp),
PARAM_BUF_PTR(in_str_params->a),
PARAM_BUF_LEN(in_str_params->a));
fp_init_from_buf(&tmp_b, &(out_params->ec_fp),
PARAM_BUF_PTR(in_str_params->b),
PARAM_BUF_LEN(in_str_params->b));
/*
* Now we can store the number of points in the group generated
* by g and the associated cofactor (i.e. npoints / order).
*/
nn_init_from_buf(&tmp_order,
PARAM_BUF_PTR(in_str_params->gen_order),
PARAM_BUF_LEN(in_str_params->gen_order));
nn_init(&(out_params->ec_gen_order), tmp_order.wlen * WORD_BYTES);
nn_copy(&(out_params->ec_gen_order), &tmp_order);
nn_init_from_buf(&tmp_order_bitlen,
PARAM_BUF_PTR(in_str_params->gen_order_bitlen),
PARAM_BUF_LEN(in_str_params->gen_order_bitlen));
out_params->ec_gen_order_bitlen = (bitcnt_t)(tmp_order_bitlen.val[0]);
nn_init_from_buf(&tmp_cofactor,
PARAM_BUF_PTR(in_str_params->cofactor),
PARAM_BUF_LEN(in_str_params->cofactor));
nn_init(&(out_params->ec_gen_cofactor),
tmp_cofactor.wlen * WORD_BYTES);
nn_copy(&(out_params->ec_gen_cofactor), &tmp_cofactor);
/* Now we can store the number of points on the curve */
nn_init_from_buf(&tmp_curve_order,
PARAM_BUF_PTR(in_str_params->curve_order),
PARAM_BUF_LEN(in_str_params->curve_order));
/* Now, we can create curve context from a and b. */
ec_shortw_crv_init(&(out_params->ec_curve), &tmp_a, &tmp_b, &tmp_curve_order);
/* Let's now import G from its affine coordinates (gx,gy) */
fp_init_from_buf(&tmp_gx, &(out_params->ec_fp),
PARAM_BUF_PTR(in_str_params->gx),
PARAM_BUF_LEN(in_str_params->gx));
fp_init_from_buf(&tmp_gy, &(out_params->ec_fp),
PARAM_BUF_PTR(in_str_params->gy),
PARAM_BUF_LEN(in_str_params->gy));
fp_init_from_buf(&tmp_gz, &(out_params->ec_fp),
PARAM_BUF_PTR(in_str_params->gz),
PARAM_BUF_LEN(in_str_params->gz));
prj_pt_init_from_coords(&(out_params->ec_gen),
&(out_params->ec_curve),
&tmp_gx, &tmp_gy, &tmp_gz);
/* Let's get the optional alpha transfert coefficients */
fp_init_from_buf(&(out_params->ec_alpha_montgomery), &(out_params->ec_fp),
PARAM_BUF_PTR(in_str_params->alpha_montgomery),
PARAM_BUF_LEN(in_str_params->alpha_montgomery));
fp_init_from_buf(&(out_params->ec_gamma_montgomery), &(out_params->ec_fp),
PARAM_BUF_PTR(in_str_params->gamma_montgomery),
PARAM_BUF_LEN(in_str_params->gamma_montgomery));
fp_init_from_buf(&(out_params->ec_alpha_edwards), &(out_params->ec_fp),
PARAM_BUF_PTR(in_str_params->alpha_edwards),
PARAM_BUF_LEN(in_str_params->alpha_edwards));
/* Import a local copy of curve OID */
MUST_HAVE(in_str_params->oid->buflen < MAX_CURVE_OID_LEN);
local_memset(out_params->curve_oid, 0, MAX_CURVE_OID_LEN);
local_strncpy((char *)out_params->curve_oid,
(const char *)in_str_params->oid->buf,
in_str_params->oid->buflen);
/* Import a local copy of curve name */
MUST_HAVE(in_str_params->name->buflen < MAX_CURVE_NAME_LEN);
local_memset(out_params->curve_name, 0, MAX_CURVE_NAME_LEN);
local_strncpy((char *)out_params->curve_name,
(const char *)in_str_params->name->buf,
in_str_params->name->buflen);
/* Get the curve type */
ec_curve_type curve_type = ec_get_curve_type_by_name(in_str_params->name->buf, in_str_params->name->buflen);
MUST_HAVE(curve_type != UNKNOWN_CURVE);
out_params->curve_type = curve_type;
/* Uninit temporary parameters */
nn_uninit(&tmp_p);
nn_uninit(&tmp_r);
nn_uninit(&tmp_r_square);
nn_uninit(&tmp_mpinv);
nn_uninit(&tmp_p_shift);
nn_uninit(&tmp_p_normalized);
nn_uninit(&tmp_p_reciprocal);
fp_uninit(&tmp_a);
fp_uninit(&tmp_b);
nn_uninit(&tmp_curve_order);
fp_uninit(&tmp_gx);
fp_uninit(&tmp_gy);
fp_uninit(&tmp_gz);
nn_uninit(&tmp_order);
nn_uninit(&tmp_cofactor);
}