/* 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.h"

#include "mpi.h"

#include "mplogic.h"

#include "mpi-priv.h"

/* Fast modular reduction for p384 = 2^384 - 2^128 - 2^96 + 2^32 - 1.  a can be r. 

 * Uses algorithm 2.30 from Hankerson, Menezes, Vanstone. Guide to 

 * Elliptic Curve Cryptography. */

static mp_err

ec_GFp_nistp384_mod(const mp_int *a, mp_int *r, const GFMethod *meth)

{

	mp_err res = MP_OKAY;

	int a_bits = mpl_significant_bits(a);

	int i;

	/* m1, m2 are statically-allocated mp_int of exactly the size we need */

	mp_int m[10];

#ifdef ECL_THIRTY_TWO_BIT

	mp_digit s[10][12];

	for (i = 0; i < 10; i++) {

		MP_SIGN(&m[i]) = MP_ZPOS;

		MP_ALLOC(&m[i]) = 12;

		MP_USED(&m[i]) = 12;

		MP_DIGITS(&m[i]) = s[i];

	}

#else

	mp_digit s[10][6];

	for (i = 0; i < 10; i++) {

		MP_SIGN(&m[i]) = MP_ZPOS;

		MP_ALLOC(&m[i]) = 6;

		MP_USED(&m[i]) = 6;

		MP_DIGITS(&m[i]) = s[i];

	}

#endif

#ifdef ECL_THIRTY_TWO_BIT

	/* for polynomials larger than twice the field size or polynomials 

	 * not using all words, use regular reduction */

	if ((a_bits > 768) || (a_bits <= 736)) {

		MP_CHECKOK(mp_mod(a, &meth->irr, r));

	} else {

		for (i = 0; i < 12; i++) {

			s[0][i] = MP_DIGIT(a, i);

		}

		s[1][0] = 0;

		s[1][1] = 0;

		s[1][2] = 0;

		s[1][3] = 0;

		s[1][4] = MP_DIGIT(a, 21);

		s[1][5] = MP_DIGIT(a, 22);

		s[1][6] = MP_DIGIT(a, 23);

		s[1][7] = 0;

		s[1][8] = 0;

		s[1][9] = 0;

		s[1][10] = 0;

		s[1][11] = 0;

		for (i = 0; i < 12; i++) {

			s[2][i] = MP_DIGIT(a, i+12);

		}

		s[3][0] = MP_DIGIT(a, 21);

		s[3][1] = MP_DIGIT(a, 22);

		s[3][2] = MP_DIGIT(a, 23);

		for (i = 3; i < 12; i++) {

			s[3][i] = MP_DIGIT(a, i+9);

		}

		s[4][0] = 0;

		s[4][1] = MP_DIGIT(a, 23);

		s[4][2] = 0;

		s[4][3] = MP_DIGIT(a, 20);

		for (i = 4; i < 12; i++) {

			s[4][i] = MP_DIGIT(a, i+8);

		}

		s[5][0] = 0;

		s[5][1] = 0;

		s[5][2] = 0;

		s[5][3] = 0;

		s[5][4] = MP_DIGIT(a, 20);

		s[5][5] = MP_DIGIT(a, 21);

		s[5][6] = MP_DIGIT(a, 22);

		s[5][7] = MP_DIGIT(a, 23);

		s[5][8] = 0;

		s[5][9] = 0;

		s[5][10] = 0;

		s[5][11] = 0;

		s[6][0] = MP_DIGIT(a, 20);

		s[6][1] = 0;

		s[6][2] = 0;

		s[6][3] = MP_DIGIT(a, 21);

		s[6][4] = MP_DIGIT(a, 22);

		s[6][5] = MP_DIGIT(a, 23);

		s[6][6] = 0;

		s[6][7] = 0;

		s[6][8] = 0;

		s[6][9] = 0;

		s[6][10] = 0;

		s[6][11] = 0;

		s[7][0] = MP_DIGIT(a, 23);

		for (i = 1; i < 12; i++) {

			s[7][i] = MP_DIGIT(a, i+11);

		}

		s[8][0] = 0;

		s[8][1] = MP_DIGIT(a, 20);

		s[8][2] = MP_DIGIT(a, 21);

		s[8][3] = MP_DIGIT(a, 22);

		s[8][4] = MP_DIGIT(a, 23);

		s[8][5] = 0;

		s[8][6] = 0;

		s[8][7] = 0;

		s[8][8] = 0;

		s[8][9] = 0;

		s[8][10] = 0;

		s[8][11] = 0;

		s[9][0] = 0;

		s[9][1] = 0;

		s[9][2] = 0;

		s[9][3] = MP_DIGIT(a, 23);

		s[9][4] = MP_DIGIT(a, 23);

		s[9][5] = 0;

		s[9][6] = 0;

		s[9][7] = 0;

		s[9][8] = 0;

		s[9][9] = 0;

		s[9][10] = 0;

		s[9][11] = 0;

		MP_CHECKOK(mp_add(&m[0], &m[1], r));

		MP_CHECKOK(mp_add(r, &m[1], r));

		MP_CHECKOK(mp_add(r, &m[2], r));

		MP_CHECKOK(mp_add(r, &m[3], r));

		MP_CHECKOK(mp_add(r, &m[4], r));

		MP_CHECKOK(mp_add(r, &m[5], r));

		MP_CHECKOK(mp_add(r, &m[6], r));

		MP_CHECKOK(mp_sub(r, &m[7], r));

		MP_CHECKOK(mp_sub(r, &m[8], r));

		MP_CHECKOK(mp_submod(r, &m[9], &meth->irr, r));

		s_mp_clamp(r);

	}

#else

	/* for polynomials larger than twice the field size or polynomials 

	 * not using all words, use regular reduction */

	if ((a_bits > 768) || (a_bits <= 736)) {

		MP_CHECKOK(mp_mod(a, &meth->irr, r));

	} else {

		for (i = 0; i < 6; i++) {

			s[0][i] = MP_DIGIT(a, i);

		}

		s[1][0] = 0;

		s[1][1] = 0;

		s[1][2] = (MP_DIGIT(a, 10) >> 32) | (MP_DIGIT(a, 11) << 32);

		s[1][3] = MP_DIGIT(a, 11) >> 32;

		s[1][4] = 0;

		s[1][5] = 0;

		for (i = 0; i < 6; i++) {

			s[2][i] = MP_DIGIT(a, i+6);

		}

		s[3][0] = (MP_DIGIT(a, 10) >> 32) | (MP_DIGIT(a, 11) << 32);

		s[3][1] = (MP_DIGIT(a, 11) >> 32) | (MP_DIGIT(a, 6) << 32);

		for (i = 2; i < 6; i++) {

			s[3][i] = (MP_DIGIT(a, i+4) >> 32) | (MP_DIGIT(a, i+5) << 32);

		}

		s[4][0] = (MP_DIGIT(a, 11) >> 32) << 32;

		s[4][1] = MP_DIGIT(a, 10) << 32;

		for (i = 2; i < 6; i++) {

			s[4][i] = MP_DIGIT(a, i+4);

		}

		s[5][0] = 0;

		s[5][1] = 0;

		s[5][2] = MP_DIGIT(a, 10);

		s[5][3] = MP_DIGIT(a, 11);

		s[5][4] = 0;

		s[5][5] = 0;

		s[6][0] = (MP_DIGIT(a, 10) << 32) >> 32;

		s[6][1] = (MP_DIGIT(a, 10) >> 32) << 32;

		s[6][2] = MP_DIGIT(a, 11);

		s[6][3] = 0;

		s[6][4] = 0;

		s[6][5] = 0;

		s[7][0] = (MP_DIGIT(a, 11) >> 32) | (MP_DIGIT(a, 6) << 32);

		for (i = 1; i < 6; i++) {

			s[7][i] = (MP_DIGIT(a, i+5) >> 32) | (MP_DIGIT(a, i+6) << 32);

		}

		s[8][0] = MP_DIGIT(a, 10) << 32;

		s[8][1] = (MP_DIGIT(a, 10) >> 32) | (MP_DIGIT(a, 11) << 32);

		s[8][2] = MP_DIGIT(a, 11) >> 32;

		s[8][3] = 0;

		s[8][4] = 0;

		s[8][5] = 0;

		s[9][0] = 0;

		s[9][1] = (MP_DIGIT(a, 11) >> 32) << 32;

		s[9][2] = MP_DIGIT(a, 11) >> 32;

		s[9][3] = 0;

		s[9][4] = 0;

		s[9][5] = 0;

		MP_CHECKOK(mp_add(&m[0], &m[1], r));

		MP_CHECKOK(mp_add(r, &m[1], r));

		MP_CHECKOK(mp_add(r, &m[2], r));

		MP_CHECKOK(mp_add(r, &m[3], r));

		MP_CHECKOK(mp_add(r, &m[4], r));

		MP_CHECKOK(mp_add(r, &m[5], r));

		MP_CHECKOK(mp_add(r, &m[6], r));

		MP_CHECKOK(mp_sub(r, &m[7], r));

		MP_CHECKOK(mp_sub(r, &m[8], r));

		MP_CHECKOK(mp_submod(r, &m[9], &meth->irr, r));

		s_mp_clamp(r);

	}

#endif

  CLEANUP:

	return res;

}

/* Compute the square of polynomial a, reduce modulo p384. Store the

 * result in r.  r could be a.  Uses optimized modular reduction for p384. 

 */

static mp_err

ec_GFp_nistp384_sqr(const mp_int *a, mp_int *r, const GFMethod *meth)

{

	mp_err res = MP_OKAY;

	MP_CHECKOK(mp_sqr(a, r));

	MP_CHECKOK(ec_GFp_nistp384_mod(r, r, meth));

  CLEANUP:

	return res;

}

/* Compute the product of two polynomials a and b, reduce modulo p384.

 * Store the result in r.  r could be a or b; a could be b.  Uses

 * optimized modular reduction for p384. */

static mp_err

ec_GFp_nistp384_mul(const mp_int *a, const mp_int *b, mp_int *r,

					const GFMethod *meth)

{

	mp_err res = MP_OKAY;

	MP_CHECKOK(mp_mul(a, b, r));

	MP_CHECKOK(ec_GFp_nistp384_mod(r, r, meth));

  CLEANUP:

	return res;

}

/* Wire in fast field arithmetic and precomputation of base point for

 * named curves. */

mp_err

ec_group_set_gfp384(ECGroup *group, ECCurveName name)

{

	if (name == ECCurve_NIST_P384) {

		group->meth->field_mod = &ec_GFp_nistp384_mod;

		group->meth->field_mul = &ec_GFp_nistp384_mul;

		group->meth->field_sqr = &ec_GFp_nistp384_sqr;

	}

	return MP_OKAY;

}