mirror of
http://galexander.org/git/simplesshd.git
synced 2024-11-15 19:48:56 +00:00
111 lines
2.6 KiB
C
111 lines
2.6 KiB
C
|
#include "tommath_private.h"
|
||
|
|
#ifdef BN_S_MP_KARATSUBA_SQR_C
|
||
|
|
/* LibTomMath, multiple-precision integer library -- Tom St Denis */
|
||
|
|
/* SPDX-License-Identifier: Unlicense */
|
||
|
|
|
||
|
|
/* Karatsuba squaring, computes b = a*a using three
|
||
|
|
* half size squarings
|
||
|
|
*
|
||
|
|
* See comments of karatsuba_mul for details. It
|
||
|
|
* is essentially the same algorithm but merely
|
||
|
|
* tuned to perform recursive squarings.
|
||
|
|
*/
|
||
|
|
mp_err s_mp_karatsuba_sqr(const mp_int *a, mp_int *b)
|
||
|
|
{
|
||
|
|
mp_int x0, x1, t1, t2, x0x0, x1x1;
|
||
|
|
int B;
|
||
|
|
mp_err err = MP_MEM;
|
||
|
|
|
||
|
|
/* min # of digits */
|
||
|
|
B = a->used;
|
||
|
|
|
||
|
|
/* now divide in two */
|
||
|
|
B = B >> 1;
|
||
|
|
|
||
|
|
/* init copy all the temps */
|
||
|
|
if (mp_init_size(&x0, B) != MP_OKAY)
|
||
|
|
goto LBL_ERR;
|
||
|
|
if (mp_init_size(&x1, a->used - B) != MP_OKAY)
|
||
|
|
goto X0;
|
||
|
|
|
||
|
|
/* init temps */
|
||
|
|
if (mp_init_size(&t1, a->used * 2) != MP_OKAY)
|
||
|
|
goto X1;
|
||
|
|
if (mp_init_size(&t2, a->used * 2) != MP_OKAY)
|
||
|
|
goto T1;
|
||
|
|
if (mp_init_size(&x0x0, B * 2) != MP_OKAY)
|
||
|
|
goto T2;
|
||
|
|
if (mp_init_size(&x1x1, (a->used - B) * 2) != MP_OKAY)
|
||
|
|
goto X0X0;
|
||
|
|
|
||
|
|
{
|
||
|
|
int x;
|
||
|
|
mp_digit *dst, *src;
|
||
|
|
|
||
|
|
src = a->dp;
|
||
|
|
|
||
|
|
/* now shift the digits */
|
||
|
|
dst = x0.dp;
|
||
|
|
for (x = 0; x < B; x++) {
|
||
|
|
*dst++ = *src++;
|
||
|
|
}
|
||
|
|
|
||
|
|
dst = x1.dp;
|
||
|
|
for (x = B; x < a->used; x++) {
|
||
|
|
*dst++ = *src++;
|
||
|
|
}
|
||
|
|
}
|
||
|
|
|
||
|
|
x0.used = B;
|
||
|
|
x1.used = a->used - B;
|
||
|
|
|
||
|
|
mp_clamp(&x0);
|
||
|
|
|
||
|
|
/* now calc the products x0*x0 and x1*x1 */
|
||
|
|
if (mp_sqr(&x0, &x0x0) != MP_OKAY)
|
||
|
|
goto X1X1; /* x0x0 = x0*x0 */
|
||
|
|
if (mp_sqr(&x1, &x1x1) != MP_OKAY)
|
||
|
|
goto X1X1; /* x1x1 = x1*x1 */
|
||
|
|
|
||
|
|
/* now calc (x1+x0)**2 */
|
||
|
|
if (s_mp_add(&x1, &x0, &t1) != MP_OKAY)
|
||
|
|
goto X1X1; /* t1 = x1 - x0 */
|
||
|
|
if (mp_sqr(&t1, &t1) != MP_OKAY)
|
||
|
|
goto X1X1; /* t1 = (x1 - x0) * (x1 - x0) */
|
||
|
|
|
||
|
|
/* add x0y0 */
|
||
|
|
if (s_mp_add(&x0x0, &x1x1, &t2) != MP_OKAY)
|
||
|
|
goto X1X1; /* t2 = x0x0 + x1x1 */
|
||
|
|
if (s_mp_sub(&t1, &t2, &t1) != MP_OKAY)
|
||
|
|
goto X1X1; /* t1 = (x1+x0)**2 - (x0x0 + x1x1) */
|
||
|
|
|
||
|
|
/* shift by B */
|
||
|
|
if (mp_lshd(&t1, B) != MP_OKAY)
|
||
|
|
goto X1X1; /* t1 = (x0x0 + x1x1 - (x1-x0)*(x1-x0))<<B */
|
||
|
|
if (mp_lshd(&x1x1, B * 2) != MP_OKAY)
|
||
|
|
goto X1X1; /* x1x1 = x1x1 << 2*B */
|
||
|
|
|
||
|
|
if (mp_add(&x0x0, &t1, &t1) != MP_OKAY)
|
||
|
|
goto X1X1; /* t1 = x0x0 + t1 */
|
||
|
|
if (mp_add(&t1, &x1x1, b) != MP_OKAY)
|
||
|
|
goto X1X1; /* t1 = x0x0 + t1 + x1x1 */
|
||
|
|
|
||
|
|
err = MP_OKAY;
|
||
|
|
|
||
|
|
X1X1:
|
||
|
|
mp_clear(&x1x1);
|
||
|
|
X0X0:
|
||
|
|
mp_clear(&x0x0);
|
||
|
|
T2:
|
||
|
|
mp_clear(&t2);
|
||
|
|
T1:
|
||
|
|
mp_clear(&t1);
|
||
|
|
X1:
|
||
|
|
mp_clear(&x1);
|
||
|
|
X0:
|
||
|
|
mp_clear(&x0);
|
||
|
|
LBL_ERR:
|
||
|
|
return err;
|
||
|
|
}
|
||
|
|
#endif
|