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#include <tommath.h>
#ifdef BN_MP_TOOM_SQR_C
/* LibTomMath, multiple-precision integer library -- Tom St Denis
*
* LibTomMath is a library that provides multiple-precision
* integer arithmetic as well as number theoretic functionality.
*
* The library was designed directly after the MPI library by
* Michael Fromberger but has been written from scratch with
* additional optimizations in place.
*
* The library is free for all purposes without any express
* guarantee it works.
*
* Tom St Denis, tomstdenis@gmail.com, http://libtom.org
*/
/* squaring using Toom-Cook 3-way algorithm */
int mp_toom_sqr(mp_int * a, mp_int * b)
{
mp_int w0, w1, w2, w3, w4, tmp1, a0, a1, a2;
int res, B;
/* init temps */
if ((res =
mp_init_multi(&w0, &w1, &w2, &w3, &w4, &a0, &a1, &a2, &tmp1,
NULL)) != MP_OKAY) {
return res;
}
/* B */
B = a->used / 3;
/* a = a2 * B**2 + a1 * B + a0 */
if ((res = mp_mod_2d(a, DIGIT_BIT * B, &a0)) != MP_OKAY) {
goto ERR;
}
if ((res = mp_copy(a, &a1)) != MP_OKAY) {
goto ERR;
}
mp_rshd(&a1, B);
mp_mod_2d(&a1, DIGIT_BIT * B, &a1);
if ((res = mp_copy(a, &a2)) != MP_OKAY) {
goto ERR;
}
mp_rshd(&a2, B * 2);
/* w0 = a0*a0 */
if ((res = mp_sqr(&a0, &w0)) != MP_OKAY) {
goto ERR;
}
/* w4 = a2 * a2 */
if ((res = mp_sqr(&a2, &w4)) != MP_OKAY) {
goto ERR;
}
/* w1 = (a2 + 2(a1 + 2a0))**2 */
if ((res = mp_mul_2(&a0, &tmp1)) != MP_OKAY) {
goto ERR;
}
if ((res = mp_add(&tmp1, &a1, &tmp1)) != MP_OKAY) {
goto ERR;
}
if ((res = mp_mul_2(&tmp1, &tmp1)) != MP_OKAY) {
goto ERR;
}
if ((res = mp_add(&tmp1, &a2, &tmp1)) != MP_OKAY) {
goto ERR;
}
if ((res = mp_sqr(&tmp1, &w1)) != MP_OKAY) {
goto ERR;
}
/* w3 = (a0 + 2(a1 + 2a2))**2 */
if ((res = mp_mul_2(&a2, &tmp1)) != MP_OKAY) {
goto ERR;
}
if ((res = mp_add(&tmp1, &a1, &tmp1)) != MP_OKAY) {
goto ERR;
}
if ((res = mp_mul_2(&tmp1, &tmp1)) != MP_OKAY) {
goto ERR;
}
if ((res = mp_add(&tmp1, &a0, &tmp1)) != MP_OKAY) {
goto ERR;
}
if ((res = mp_sqr(&tmp1, &w3)) != MP_OKAY) {
goto ERR;
}
/* w2 = (a2 + a1 + a0)**2 */
if ((res = mp_add(&a2, &a1, &tmp1)) != MP_OKAY) {
goto ERR;
}
if ((res = mp_add(&tmp1, &a0, &tmp1)) != MP_OKAY) {
goto ERR;
}
if ((res = mp_sqr(&tmp1, &w2)) != MP_OKAY) {
goto ERR;
}
/* now solve the matrix
0 0 0 0 1
1 2 4 8 16
1 1 1 1 1
16 8 4 2 1
1 0 0 0 0
using 12 subtractions, 4 shifts, 2 small divisions and 1 small multiplication.
*/
/* r1 - r4 */
if ((res = mp_sub(&w1, &w4, &w1)) != MP_OKAY) {
goto ERR;
}
/* r3 - r0 */
if ((res = mp_sub(&w3, &w0, &w3)) != MP_OKAY) {
goto ERR;
}
/* r1/2 */
if ((res = mp_div_2(&w1, &w1)) != MP_OKAY) {
goto ERR;
}
/* r3/2 */
if ((res = mp_div_2(&w3, &w3)) != MP_OKAY) {
goto ERR;
}
/* r2 - r0 - r4 */
if ((res = mp_sub(&w2, &w0, &w2)) != MP_OKAY) {
goto ERR;
}
if ((res = mp_sub(&w2, &w4, &w2)) != MP_OKAY) {
goto ERR;
}
/* r1 - r2 */
if ((res = mp_sub(&w1, &w2, &w1)) != MP_OKAY) {
goto ERR;
}
/* r3 - r2 */
if ((res = mp_sub(&w3, &w2, &w3)) != MP_OKAY) {
goto ERR;
}
/* r1 - 8r0 */
if ((res = mp_mul_2d(&w0, 3, &tmp1)) != MP_OKAY) {
goto ERR;
}
if ((res = mp_sub(&w1, &tmp1, &w1)) != MP_OKAY) {
goto ERR;
}
/* r3 - 8r4 */
if ((res = mp_mul_2d(&w4, 3, &tmp1)) != MP_OKAY) {
goto ERR;
}
if ((res = mp_sub(&w3, &tmp1, &w3)) != MP_OKAY) {
goto ERR;
}
/* 3r2 - r1 - r3 */
if ((res = mp_mul_d(&w2, 3, &w2)) != MP_OKAY) {
goto ERR;
}
if ((res = mp_sub(&w2, &w1, &w2)) != MP_OKAY) {
goto ERR;
}
if ((res = mp_sub(&w2, &w3, &w2)) != MP_OKAY) {
goto ERR;
}
/* r1 - r2 */
if ((res = mp_sub(&w1, &w2, &w1)) != MP_OKAY) {
goto ERR;
}
/* r3 - r2 */
if ((res = mp_sub(&w3, &w2, &w3)) != MP_OKAY) {
goto ERR;
}
/* r1/3 */
if ((res = mp_div_3(&w1, &w1, NULL)) != MP_OKAY) {
goto ERR;
}
/* r3/3 */
if ((res = mp_div_3(&w3, &w3, NULL)) != MP_OKAY) {
goto ERR;
}
/* at this point shift W[n] by B*n */
if ((res = mp_lshd(&w1, 1 * B)) != MP_OKAY) {
goto ERR;
}
if ((res = mp_lshd(&w2, 2 * B)) != MP_OKAY) {
goto ERR;
}
if ((res = mp_lshd(&w3, 3 * B)) != MP_OKAY) {
goto ERR;
}
if ((res = mp_lshd(&w4, 4 * B)) != MP_OKAY) {
goto ERR;
}
if ((res = mp_add(&w0, &w1, b)) != MP_OKAY) {
goto ERR;
}
if ((res = mp_add(&w2, &w3, &tmp1)) != MP_OKAY) {
goto ERR;
}
if ((res = mp_add(&w4, &tmp1, &tmp1)) != MP_OKAY) {
goto ERR;
}
if ((res = mp_add(&tmp1, b, b)) != MP_OKAY) {
goto ERR;
}
ERR:
mp_clear_multi(&w0, &w1, &w2, &w3, &w4, &a0, &a1, &a2, &tmp1, NULL);
return res;
}
#endif
/* $Source: /cvs/libtom/libtommath/bn_mp_toom_sqr.c,v $ */
/* $Revision: 1.4 $ */
/* $Date: 2006/12/28 01:25:13 $ */
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