The Tor Browser: security/nss/lib/freebl/ecl/ecp

Incorporate requested changes from Mozilla in review:
https://bugzilla.mozilla.org/show_bug.cgi?id=1123480#c6

     1 /* This Source Code Form is subject to the terms of the Mozilla Public

     2  * License, v. 2.0. If a copy of the MPL was not distributed with this

     3  * file, You can obtain one at http://mozilla.org/MPL/2.0/. */

     5 #include "ecp_fp.h"

     6 #include <stdlib.h>

     8 #define ECFP_BSIZE 160

     9 #define ECFP_NUMDOUBLES 7

    11 #include "ecp_fpinc.c"

    13 /* Performs a single step of reduction, just on the uppermost float

    14  * (assumes already tidied), and then retidies. Note, this does not

    15  * guarantee that the result will be less than p, but truncates the number

    16  * of bits. */

    17 void

    18 ecfp160_singleReduce(double *d, const EC_group_fp * group)

    19 {

    20 	double q;

    22 	ECFP_ASSERT(group->doubleBitSize == 24);

    23 	ECFP_ASSERT(group->primeBitSize == 160);

    24 	ECFP_ASSERT(ECFP_NUMDOUBLES == 7);

    26 	q = d[ECFP_NUMDOUBLES - 1] - ecfp_beta_160;

    27 	q += group->bitSize_alpha;

    28 	q -= group->bitSize_alpha;

    30 	d[ECFP_NUMDOUBLES - 1] -= q;

    31 	d[0] += q * ecfp_twom160;

    32 	d[1] += q * ecfp_twom129;

    33 	ecfp_positiveTidy(d, group);

    35 	/* Assertions for the highest order term */

    36 	ECFP_ASSERT(d[ECFP_NUMDOUBLES - 1] / ecfp_exp[ECFP_NUMDOUBLES - 1] ==

    37 				(unsigned long long) (d[ECFP_NUMDOUBLES - 1] /

    38 									  ecfp_exp[ECFP_NUMDOUBLES - 1]));

    39 	ECFP_ASSERT(d[ECFP_NUMDOUBLES - 1] >= 0);

    40 }

    42 /* Performs imperfect reduction.  This might leave some negative terms,

    43  * and one more reduction might be required for the result to be between 0

    44  * and p-1. x should not already be reduced, i.e. should have

    45  * 2*ECFP_NUMDOUBLES significant terms. x and r can be the same, but then

    46  * the upper parts of r are not zeroed */

    47 void

    48 ecfp160_reduce(double *r, double *x, const EC_group_fp * group)

    49 {

    51 	double x7, x8, q;

    53 	ECFP_ASSERT(group->doubleBitSize == 24);

    54 	ECFP_ASSERT(group->primeBitSize == 160);

    55 	ECFP_ASSERT(ECFP_NUMDOUBLES == 7);

    57 	/* Tidy just the upper bits, the lower bits can wait. */

    58 	ecfp_tidyUpper(x, group);

    60 	/* Assume that this is already tidied so that we have enough extra

    61 	 * bits */

    62 	x7 = x[7] + x[13] * ecfp_twom129;	/* adds bits 15-39 */

    64 	/* Tidy x7, or we won't have enough bits later to add it in */

    65 	q = x7 + group->alpha[8];

    66 	q -= group->alpha[8];

    67 	x7 -= q;					/* holds bits 0-24 */

    68 	x8 = x[8] + q;				/* holds bits 0-25 */

    70 	r[6] = x[6] + x[13] * ecfp_twom160 + x[12] * ecfp_twom129;	/* adds

    71 																 * bits

    72 																 * 8-39 */

    73 	r[5] = x[5] + x[12] * ecfp_twom160 + x[11] * ecfp_twom129;

    74 	r[4] = x[4] + x[11] * ecfp_twom160 + x[10] * ecfp_twom129;

    75 	r[3] = x[3] + x[10] * ecfp_twom160 + x[9] * ecfp_twom129;

    76 	r[2] = x[2] + x[9] * ecfp_twom160 + x8 * ecfp_twom129;	/* adds bits

    77 															 * 8-40 */

    78 	r[1] = x[1] + x8 * ecfp_twom160 + x7 * ecfp_twom129;	/* adds bits

    79 															 * 8-39 */

    80 	r[0] = x[0] + x7 * ecfp_twom160;

    82 	/* Tidy up just r[ECFP_NUMDOUBLES-2] so that the number of reductions

    83 	 * is accurate plus or minus one.  (Rather than tidy all to make it

    84 	 * totally accurate, which is more costly.) */

    85 	q = r[ECFP_NUMDOUBLES - 2] + group->alpha[ECFP_NUMDOUBLES - 1];

    86 	q -= group->alpha[ECFP_NUMDOUBLES - 1];

    87 	r[ECFP_NUMDOUBLES - 2] -= q;

    88 	r[ECFP_NUMDOUBLES - 1] += q;

    90 	/* Tidy up the excess bits on r[ECFP_NUMDOUBLES-1] using reduction */

    91 	/* Use ecfp_beta so we get a positive result */

    92 	q = r[ECFP_NUMDOUBLES - 1] - ecfp_beta_160;

    93 	q += group->bitSize_alpha;

    94 	q -= group->bitSize_alpha;

    96 	r[ECFP_NUMDOUBLES - 1] -= q;

    97 	r[0] += q * ecfp_twom160;

    98 	r[1] += q * ecfp_twom129;

   100 	/* Tidy the result */

   101 	ecfp_tidyShort(r, group);

   102 }

   104 /* Sets group to use optimized calculations in this file */

   105 mp_err

   106 ec_group_set_secp160r1_fp(ECGroup *group)

   107 {

   109 	EC_group_fp *fpg = NULL;

   111 	/* Allocate memory for floating point group data */

   112 	fpg = (EC_group_fp *) malloc(sizeof(EC_group_fp));

   113 	if (fpg == NULL) {

   114 		return MP_MEM;

   115 	}

   117 	fpg->numDoubles = ECFP_NUMDOUBLES;

   118 	fpg->primeBitSize = ECFP_BSIZE;

   119 	fpg->orderBitSize = 161;

   120 	fpg->doubleBitSize = 24;

   121 	fpg->numInts = (ECFP_BSIZE + ECL_BITS - 1) / ECL_BITS;

   122 	fpg->aIsM3 = 1;

   123 	fpg->ecfp_singleReduce = &ecfp160_singleReduce;

   124 	fpg->ecfp_reduce = &ecfp160_reduce;

   125 	fpg->ecfp_tidy = &ecfp_tidy;

   127 	fpg->pt_add_jac_aff = &ecfp160_pt_add_jac_aff;

   128 	fpg->pt_add_jac = &ecfp160_pt_add_jac;

   129 	fpg->pt_add_jm_chud = &ecfp160_pt_add_jm_chud;

   130 	fpg->pt_add_chud = &ecfp160_pt_add_chud;

   131 	fpg->pt_dbl_jac = &ecfp160_pt_dbl_jac;

   132 	fpg->pt_dbl_jm = &ecfp160_pt_dbl_jm;

   133 	fpg->pt_dbl_aff2chud = &ecfp160_pt_dbl_aff2chud;

   134 	fpg->precompute_chud = &ecfp160_precompute_chud;

   135 	fpg->precompute_jac = &ecfp160_precompute_jac;

   137 	group->point_mul = &ec_GFp_point_mul_wNAF_fp;

   138 	group->points_mul = &ec_pts_mul_basic;

   139 	group->extra1 = fpg;

   140 	group->extra_free = &ec_GFp_extra_free_fp;

   142 	ec_set_fp_precision(fpg);

   143 	fpg->bitSize_alpha = ECFP_TWO160 * fpg->alpha[0];

   144 	return MP_OKAY;

   145 }

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