*

 *

 *

 *

 * The Original Code is the elliptic curve math library for binary polynomial field curves.

 *

 * The Initial Developer of the Original Code is

 * Sun Microsystems, Inc.

 * Portions created by the Initial Developer are Copyright (C) 2003

 * the Initial Developer. All Rights Reserved.

 *

 * Contributor(s):

 *   Sheueling Chang-Shantz <sheueling.chang@sun.com>,

 *   Stephen Fung <fungstep@hotmail.com>, and

 *   Douglas Stebila <douglas@stebila.ca>, Sun Microsystems Laboratories.

 *

 *********************************************************************** */

#include "ec2.h"

#include "mp_gf2m.h"

#include "mp_gf2m-priv.h"

#include "mpi.h"

#include "mpi-priv.h"

#ifndef _KERNEL

#include <stdlib.h>

#endif

/* 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;

}