mirror of
https://github.com/rn10950/RetroZilla.git
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146 lines
4.6 KiB
C
146 lines
4.6 KiB
C
/* This Source Code Form is subject to the terms of the Mozilla Public
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* License, v. 2.0. If a copy of the MPL was not distributed with this
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* file, You can obtain one at http://mozilla.org/MPL/2.0/. */
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#include "ecp_fp.h"
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#include <stdlib.h>
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#define ECFP_BSIZE 160
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#define ECFP_NUMDOUBLES 7
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#include "ecp_fpinc.c"
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/* Performs a single step of reduction, just on the uppermost float
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* (assumes already tidied), and then retidies. Note, this does not
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* guarantee that the result will be less than p, but truncates the number
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* of bits. */
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void
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ecfp160_singleReduce(double *d, const EC_group_fp * group)
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{
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double q;
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ECFP_ASSERT(group->doubleBitSize == 24);
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ECFP_ASSERT(group->primeBitSize == 160);
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ECFP_ASSERT(ECFP_NUMDOUBLES == 7);
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q = d[ECFP_NUMDOUBLES - 1] - ecfp_beta_160;
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q += group->bitSize_alpha;
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q -= group->bitSize_alpha;
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d[ECFP_NUMDOUBLES - 1] -= q;
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d[0] += q * ecfp_twom160;
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d[1] += q * ecfp_twom129;
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ecfp_positiveTidy(d, group);
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/* Assertions for the highest order term */
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ECFP_ASSERT(d[ECFP_NUMDOUBLES - 1] / ecfp_exp[ECFP_NUMDOUBLES - 1] ==
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(unsigned long long) (d[ECFP_NUMDOUBLES - 1] /
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ecfp_exp[ECFP_NUMDOUBLES - 1]));
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ECFP_ASSERT(d[ECFP_NUMDOUBLES - 1] >= 0);
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}
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/* Performs imperfect reduction. This might leave some negative terms,
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* and one more reduction might be required for the result to be between 0
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* and p-1. x should not already be reduced, i.e. should have
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* 2*ECFP_NUMDOUBLES significant terms. x and r can be the same, but then
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* the upper parts of r are not zeroed */
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void
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ecfp160_reduce(double *r, double *x, const EC_group_fp * group)
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{
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double x7, x8, q;
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ECFP_ASSERT(group->doubleBitSize == 24);
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ECFP_ASSERT(group->primeBitSize == 160);
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ECFP_ASSERT(ECFP_NUMDOUBLES == 7);
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/* Tidy just the upper bits, the lower bits can wait. */
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ecfp_tidyUpper(x, group);
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/* Assume that this is already tidied so that we have enough extra
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* bits */
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x7 = x[7] + x[13] * ecfp_twom129; /* adds bits 15-39 */
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/* Tidy x7, or we won't have enough bits later to add it in */
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q = x7 + group->alpha[8];
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q -= group->alpha[8];
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x7 -= q; /* holds bits 0-24 */
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x8 = x[8] + q; /* holds bits 0-25 */
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r[6] = x[6] + x[13] * ecfp_twom160 + x[12] * ecfp_twom129; /* adds
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* bits
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* 8-39 */
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r[5] = x[5] + x[12] * ecfp_twom160 + x[11] * ecfp_twom129;
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r[4] = x[4] + x[11] * ecfp_twom160 + x[10] * ecfp_twom129;
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r[3] = x[3] + x[10] * ecfp_twom160 + x[9] * ecfp_twom129;
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r[2] = x[2] + x[9] * ecfp_twom160 + x8 * ecfp_twom129; /* adds bits
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* 8-40 */
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r[1] = x[1] + x8 * ecfp_twom160 + x7 * ecfp_twom129; /* adds bits
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* 8-39 */
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r[0] = x[0] + x7 * ecfp_twom160;
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/* Tidy up just r[ECFP_NUMDOUBLES-2] so that the number of reductions
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* is accurate plus or minus one. (Rather than tidy all to make it
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* totally accurate, which is more costly.) */
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q = r[ECFP_NUMDOUBLES - 2] + group->alpha[ECFP_NUMDOUBLES - 1];
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q -= group->alpha[ECFP_NUMDOUBLES - 1];
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r[ECFP_NUMDOUBLES - 2] -= q;
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r[ECFP_NUMDOUBLES - 1] += q;
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/* Tidy up the excess bits on r[ECFP_NUMDOUBLES-1] using reduction */
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/* Use ecfp_beta so we get a positive result */
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q = r[ECFP_NUMDOUBLES - 1] - ecfp_beta_160;
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q += group->bitSize_alpha;
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q -= group->bitSize_alpha;
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r[ECFP_NUMDOUBLES - 1] -= q;
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r[0] += q * ecfp_twom160;
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r[1] += q * ecfp_twom129;
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/* Tidy the result */
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ecfp_tidyShort(r, group);
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}
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/* Sets group to use optimized calculations in this file */
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mp_err
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ec_group_set_secp160r1_fp(ECGroup *group)
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{
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EC_group_fp *fpg = NULL;
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/* Allocate memory for floating point group data */
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fpg = (EC_group_fp *) malloc(sizeof(EC_group_fp));
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if (fpg == NULL) {
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return MP_MEM;
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}
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fpg->numDoubles = ECFP_NUMDOUBLES;
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fpg->primeBitSize = ECFP_BSIZE;
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fpg->orderBitSize = 161;
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fpg->doubleBitSize = 24;
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fpg->numInts = (ECFP_BSIZE + ECL_BITS - 1) / ECL_BITS;
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fpg->aIsM3 = 1;
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fpg->ecfp_singleReduce = &ecfp160_singleReduce;
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fpg->ecfp_reduce = &ecfp160_reduce;
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fpg->ecfp_tidy = &ecfp_tidy;
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fpg->pt_add_jac_aff = &ecfp160_pt_add_jac_aff;
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fpg->pt_add_jac = &ecfp160_pt_add_jac;
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fpg->pt_add_jm_chud = &ecfp160_pt_add_jm_chud;
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fpg->pt_add_chud = &ecfp160_pt_add_chud;
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fpg->pt_dbl_jac = &ecfp160_pt_dbl_jac;
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fpg->pt_dbl_jm = &ecfp160_pt_dbl_jm;
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fpg->pt_dbl_aff2chud = &ecfp160_pt_dbl_aff2chud;
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fpg->precompute_chud = &ecfp160_precompute_chud;
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fpg->precompute_jac = &ecfp160_precompute_jac;
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group->point_mul = &ec_GFp_point_mul_wNAF_fp;
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group->points_mul = &ec_pts_mul_basic;
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group->extra1 = fpg;
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group->extra_free = &ec_GFp_extra_free_fp;
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ec_set_fp_precision(fpg);
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fpg->bitSize_alpha = ECFP_TWO160 * fpg->alpha[0];
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return MP_OKAY;
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}
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