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/* This Source Code Form is subject to the terms of the Mozilla Public
* License, v. 2.0. If a copy of the MPL was not distributed with this
* file, You can obtain one at http://mozilla.org/MPL/2.0/. */
#include "ecp_fp.h"
#include <stdlib.h>
#define ECFP_BSIZE 160
#define ECFP_NUMDOUBLES 7
#include "ecp_fpinc.c"
/* Performs a single step of reduction, just on the uppermost float
* (assumes already tidied), and then retidies. Note, this does not
* guarantee that the result will be less than p, but truncates the number
* of bits. */
void
ecfp160_singleReduce(double *d, const EC_group_fp * group)
{
double q;
ECFP_ASSERT(group->doubleBitSize == 24);
ECFP_ASSERT(group->primeBitSize == 160);
ECFP_ASSERT(ECFP_NUMDOUBLES == 7);
q = d[ECFP_NUMDOUBLES - 1] - ecfp_beta_160;
q += group->bitSize_alpha;
q -= group->bitSize_alpha;
d[ECFP_NUMDOUBLES - 1] -= q;
d[0] += q * ecfp_twom160;
d[1] += q * ecfp_twom129;
ecfp_positiveTidy(d, group);
/* Assertions for the highest order term */
ECFP_ASSERT(d[ECFP_NUMDOUBLES - 1] / ecfp_exp[ECFP_NUMDOUBLES - 1] ==
(unsigned long long) (d[ECFP_NUMDOUBLES - 1] /
ecfp_exp[ECFP_NUMDOUBLES - 1]));
ECFP_ASSERT(d[ECFP_NUMDOUBLES - 1] >= 0);
}
/* Performs imperfect reduction. This might leave some negative terms,
* and one more reduction might be required for the result to be between 0
* and p-1. x should not already be reduced, i.e. should have
* 2*ECFP_NUMDOUBLES significant terms. x and r can be the same, but then
* the upper parts of r are not zeroed */
void
ecfp160_reduce(double *r, double *x, const EC_group_fp * group)
{
double x7, x8, q;
ECFP_ASSERT(group->doubleBitSize == 24);
ECFP_ASSERT(group->primeBitSize == 160);
ECFP_ASSERT(ECFP_NUMDOUBLES == 7);
/* Tidy just the upper bits, the lower bits can wait. */
ecfp_tidyUpper(x, group);
/* Assume that this is already tidied so that we have enough extra
* bits */
x7 = x[7] + x[13] * ecfp_twom129; /* adds bits 15-39 */
/* Tidy x7, or we won't have enough bits later to add it in */
q = x7 + group->alpha[8];
q -= group->alpha[8];
x7 -= q; /* holds bits 0-24 */
x8 = x[8] + q; /* holds bits 0-25 */
r[6] = x[6] + x[13] * ecfp_twom160 + x[12] * ecfp_twom129; /* adds
* bits
* 8-39 */
r[5] = x[5] + x[12] * ecfp_twom160 + x[11] * ecfp_twom129;
r[4] = x[4] + x[11] * ecfp_twom160 + x[10] * ecfp_twom129;
r[3] = x[3] + x[10] * ecfp_twom160 + x[9] * ecfp_twom129;
r[2] = x[2] + x[9] * ecfp_twom160 + x8 * ecfp_twom129; /* adds bits
* 8-40 */
r[1] = x[1] + x8 * ecfp_twom160 + x7 * ecfp_twom129; /* adds bits
* 8-39 */
r[0] = x[0] + x7 * ecfp_twom160;
/* Tidy up just r[ECFP_NUMDOUBLES-2] so that the number of reductions
* is accurate plus or minus one. (Rather than tidy all to make it
* totally accurate, which is more costly.) */
q = r[ECFP_NUMDOUBLES - 2] + group->alpha[ECFP_NUMDOUBLES - 1];
q -= group->alpha[ECFP_NUMDOUBLES - 1];
r[ECFP_NUMDOUBLES - 2] -= q;
r[ECFP_NUMDOUBLES - 1] += q;
/* Tidy up the excess bits on r[ECFP_NUMDOUBLES-1] using reduction */
/* Use ecfp_beta so we get a positive result */
q = r[ECFP_NUMDOUBLES - 1] - ecfp_beta_160;
q += group->bitSize_alpha;
q -= group->bitSize_alpha;
r[ECFP_NUMDOUBLES - 1] -= q;
r[0] += q * ecfp_twom160;
r[1] += q * ecfp_twom129;
/* Tidy the result */
ecfp_tidyShort(r, group);
}
/* Sets group to use optimized calculations in this file */
mp_err
ec_group_set_secp160r1_fp(ECGroup *group)
{
EC_group_fp *fpg = NULL;
/* Allocate memory for floating point group data */
fpg = (EC_group_fp *) malloc(sizeof(EC_group_fp));
if (fpg == NULL) {
return MP_MEM;
}
fpg->numDoubles = ECFP_NUMDOUBLES;
fpg->primeBitSize = ECFP_BSIZE;
fpg->orderBitSize = 161;
fpg->doubleBitSize = 24;
fpg->numInts = (ECFP_BSIZE + ECL_BITS - 1) / ECL_BITS;
fpg->aIsM3 = 1;
fpg->ecfp_singleReduce = &ecfp160_singleReduce;
fpg->ecfp_reduce = &ecfp160_reduce;
fpg->ecfp_tidy = &ecfp_tidy;
fpg->pt_add_jac_aff = &ecfp160_pt_add_jac_aff;
fpg->pt_add_jac = &ecfp160_pt_add_jac;
fpg->pt_add_jm_chud = &ecfp160_pt_add_jm_chud;
fpg->pt_add_chud = &ecfp160_pt_add_chud;
fpg->pt_dbl_jac = &ecfp160_pt_dbl_jac;
fpg->pt_dbl_jm = &ecfp160_pt_dbl_jm;
fpg->pt_dbl_aff2chud = &ecfp160_pt_dbl_aff2chud;
fpg->precompute_chud = &ecfp160_precompute_chud;
fpg->precompute_jac = &ecfp160_precompute_jac;
group->point_mul = &ec_GFp_point_mul_wNAF_fp;
group->points_mul = &ec_pts_mul_basic;
group->extra1 = fpg;
group->extra_free = &ec_GFp_extra_free_fp;
ec_set_fp_precision(fpg);
fpg->bitSize_alpha = ECFP_TWO160 * fpg->alpha[0];
return MP_OKAY;
}
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