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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 "ec2.h"
#include "mp_gf2m.h"
#include "mp_gf2m-priv.h"
#include "mpi.h"
#include "mpi-priv.h"
#include <stdlib.h>

/* Fast reduction for polynomials over a 163-bit curve. Assumes reduction
 * polynomial with terms {163, 7, 6, 3, 0}. */
mp_err
ec_GF2m_163_mod(const mp_int *a, mp_int *r, const GFMethod *meth)
{
	mp_err res = MP_OKAY;
	mp_digit *u, z;

	if (a != r) {
		MP_CHECKOK(mp_copy(a, r));
	}
#ifdef ECL_SIXTY_FOUR_BIT
	if (MP_USED(r) < 6) {
		MP_CHECKOK(s_mp_pad(r, 6));
	}
	u = MP_DIGITS(r);
	MP_USED(r) = 6;

	/* u[5] only has 6 significant bits */
	z = u[5];
	u[2] ^= (z << 36) ^ (z << 35) ^ (z << 32) ^ (z << 29);
	z = u[4];
	u[2] ^= (z >> 28) ^ (z >> 29) ^ (z >> 32) ^ (z >> 35);
	u[1] ^= (z << 36) ^ (z << 35) ^ (z << 32) ^ (z << 29);
	z = u[3];
	u[1] ^= (z >> 28) ^ (z >> 29) ^ (z >> 32) ^ (z >> 35);
	u[0] ^= (z << 36) ^ (z << 35) ^ (z << 32) ^ (z << 29);
	z = u[2] >> 35;				/* z only has 29 significant bits */
	u[0] ^= (z << 7) ^ (z << 6) ^ (z << 3) ^ z;
	/* clear bits above 163 */
	u[5] = u[4] = u[3] = 0;
	u[2] ^= z << 35;
#else
	if (MP_USED(r) < 11) {
		MP_CHECKOK(s_mp_pad(r, 11));
	}
	u = MP_DIGITS(r);
	MP_USED(r) = 11;

	/* u[11] only has 6 significant bits */
	z = u[10];
	u[5] ^= (z << 4) ^ (z << 3) ^ z ^ (z >> 3);
	u[4] ^= (z << 29);
	z = u[9];
	u[5] ^= (z >> 28) ^ (z >> 29);
	u[4] ^= (z << 4) ^ (z << 3) ^ z ^ (z >> 3);
	u[3] ^= (z << 29);
	z = u[8];
	u[4] ^= (z >> 28) ^ (z >> 29);
	u[3] ^= (z << 4) ^ (z << 3) ^ z ^ (z >> 3);
	u[2] ^= (z << 29);
	z = u[7];
	u[3] ^= (z >> 28) ^ (z >> 29);
	u[2] ^= (z << 4) ^ (z << 3) ^ z ^ (z >> 3);
	u[1] ^= (z << 29);
	z = u[6];
	u[2] ^= (z >> 28) ^ (z >> 29);
	u[1] ^= (z << 4) ^ (z << 3) ^ z ^ (z >> 3);
	u[0] ^= (z << 29);
	z = u[5] >> 3;				/* z only has 29 significant bits */
	u[1] ^= (z >> 25) ^ (z >> 26);
	u[0] ^= (z << 7) ^ (z << 6) ^ (z << 3) ^ z;
	/* clear bits above 163 */
	u[11] = u[10] = u[9] = u[8] = u[7] = u[6] = 0;
	u[5] ^= z << 3;
#endif
	s_mp_clamp(r);

  CLEANUP:
	return res;
}

/* Fast squaring for polynomials over a 163-bit curve. Assumes reduction
 * polynomial with terms {163, 7, 6, 3, 0}. */
mp_err
ec_GF2m_163_sqr(const mp_int *a, mp_int *r, const GFMethod *meth)
{
	mp_err res = MP_OKAY;
	mp_digit *u, *v;

	v = MP_DIGITS(a);

#ifdef ECL_SIXTY_FOUR_BIT
	if (MP_USED(a) < 3) {
		return mp_bsqrmod(a, meth->irr_arr, r);
	}
	if (MP_USED(r) < 6) {
		MP_CHECKOK(s_mp_pad(r, 6));
	}
	MP_USED(r) = 6;
#else
	if (MP_USED(a) < 6) {
		return mp_bsqrmod(a, meth->irr_arr, r);
	}
	if (MP_USED(r) < 12) {
		MP_CHECKOK(s_mp_pad(r, 12));
	}
	MP_USED(r) = 12;
#endif
	u = MP_DIGITS(r);

#ifdef ECL_THIRTY_TWO_BIT
	u[11] = gf2m_SQR1(v[5]);
	u[10] = gf2m_SQR0(v[5]);
	u[9] = gf2m_SQR1(v[4]);
	u[8] = gf2m_SQR0(v[4]);
	u[7] = gf2m_SQR1(v[3]);
	u[6] = gf2m_SQR0(v[3]);
#endif
	u[5] = gf2m_SQR1(v[2]);
	u[4] = gf2m_SQR0(v[2]);
	u[3] = gf2m_SQR1(v[1]);
	u[2] = gf2m_SQR0(v[1]);
	u[1] = gf2m_SQR1(v[0]);
	u[0] = gf2m_SQR0(v[0]);
	return ec_GF2m_163_mod(r, r, meth);

  CLEANUP:
	return res;
}

/* Fast multiplication for polynomials over a 163-bit curve. Assumes
 * reduction polynomial with terms {163, 7, 6, 3, 0}. */
mp_err
ec_GF2m_163_mul(const mp_int *a, const mp_int *b, mp_int *r,
				const GFMethod *meth)
{
	mp_err res = MP_OKAY;
	mp_digit a2 = 0, a1 = 0, a0, b2 = 0, b1 = 0, b0;

#ifdef ECL_THIRTY_TWO_BIT
	mp_digit a5 = 0, a4 = 0, a3 = 0, b5 = 0, b4 = 0, b3 = 0;
	mp_digit rm[6];
#endif

	if (a == b) {
		return ec_GF2m_163_sqr(a, r, meth);
	} else {
		switch (MP_USED(a)) {
#ifdef ECL_THIRTY_TWO_BIT
		case 6:
			a5 = MP_DIGIT(a, 5);
		case 5:
			a4 = MP_DIGIT(a, 4);
		case 4:
			a3 = MP_DIGIT(a, 3);
#endif
		case 3:
			a2 = MP_DIGIT(a, 2);
		case 2:
			a1 = MP_DIGIT(a, 1);
		default:
			a0 = MP_DIGIT(a, 0);
		}
		switch (MP_USED(b)) {
#ifdef ECL_THIRTY_TWO_BIT
		case 6:
			b5 = MP_DIGIT(b, 5);
		case 5:
			b4 = MP_DIGIT(b, 4);
		case 4:
			b3 = MP_DIGIT(b, 3);
#endif
		case 3:
			b2 = MP_DIGIT(b, 2);
		case 2:
			b1 = MP_DIGIT(b, 1);
		default:
			b0 = MP_DIGIT(b, 0);
		}
#ifdef ECL_SIXTY_FOUR_BIT
		MP_CHECKOK(s_mp_pad(r, 6));
		s_bmul_3x3(MP_DIGITS(r), a2, a1, a0, b2, b1, b0);
		MP_USED(r) = 6;
		s_mp_clamp(r);
#else
		MP_CHECKOK(s_mp_pad(r, 12));
		s_bmul_3x3(MP_DIGITS(r) + 6, a5, a4, a3, b5, b4, b3);
		s_bmul_3x3(MP_DIGITS(r), a2, a1, a0, b2, b1, b0);
		s_bmul_3x3(rm, a5 ^ a2, a4 ^ a1, a3 ^ a0, b5 ^ b2, b4 ^ b1,
				   b3 ^ b0);
		rm[5] ^= MP_DIGIT(r, 5) ^ MP_DIGIT(r, 11);
		rm[4] ^= MP_DIGIT(r, 4) ^ MP_DIGIT(r, 10);
		rm[3] ^= MP_DIGIT(r, 3) ^ MP_DIGIT(r, 9);
		rm[2] ^= MP_DIGIT(r, 2) ^ MP_DIGIT(r, 8);
		rm[1] ^= MP_DIGIT(r, 1) ^ MP_DIGIT(r, 7);
		rm[0] ^= MP_DIGIT(r, 0) ^ MP_DIGIT(r, 6);
		MP_DIGIT(r, 8) ^= rm[5];
		MP_DIGIT(r, 7) ^= rm[4];
		MP_DIGIT(r, 6) ^= rm[3];
		MP_DIGIT(r, 5) ^= rm[2];
		MP_DIGIT(r, 4) ^= rm[1];
		MP_DIGIT(r, 3) ^= rm[0];
		MP_USED(r) = 12;
		s_mp_clamp(r);
#endif
		return ec_GF2m_163_mod(r, r, meth);
	}

  CLEANUP:
	return res;
}

/* Wire in fast field arithmetic for 163-bit curves. */
mp_err
ec_group_set_gf2m163(ECGroup *group, ECCurveName name)
{
	group->meth->field_mod = &ec_GF2m_163_mod;
	group->meth->field_mul = &ec_GF2m_163_mul;
	group->meth->field_sqr = &ec_GF2m_163_sqr;
	return MP_OKAY;
}