83 lines
2.3 KiB
C
83 lines
2.3 KiB
C
#include "tommath_private.h"
|
|
#ifdef BN_S_MP_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.
|
|
*/
|
|
|
|
/* low level squaring, b = a*a, HAC pp.596-597, Algorithm 14.16 */
|
|
int s_mp_sqr(const mp_int *a, mp_int *b)
|
|
{
|
|
mp_int t;
|
|
int res, ix, iy, pa;
|
|
mp_word r;
|
|
mp_digit u, tmpx, *tmpt;
|
|
|
|
pa = a->used;
|
|
if ((res = mp_init_size(&t, (2 * pa) + 1)) != MP_OKAY) {
|
|
return res;
|
|
}
|
|
|
|
/* default used is maximum possible size */
|
|
t.used = (2 * pa) + 1;
|
|
|
|
for (ix = 0; ix < pa; ix++) {
|
|
/* first calculate the digit at 2*ix */
|
|
/* calculate double precision result */
|
|
r = (mp_word)t.dp[2*ix] +
|
|
((mp_word)a->dp[ix] * (mp_word)a->dp[ix]);
|
|
|
|
/* store lower part in result */
|
|
t.dp[ix+ix] = (mp_digit)(r & (mp_word)MP_MASK);
|
|
|
|
/* get the carry */
|
|
u = (mp_digit)(r >> (mp_word)DIGIT_BIT);
|
|
|
|
/* left hand side of A[ix] * A[iy] */
|
|
tmpx = a->dp[ix];
|
|
|
|
/* alias for where to store the results */
|
|
tmpt = t.dp + ((2 * ix) + 1);
|
|
|
|
for (iy = ix + 1; iy < pa; iy++) {
|
|
/* first calculate the product */
|
|
r = (mp_word)tmpx * (mp_word)a->dp[iy];
|
|
|
|
/* now calculate the double precision result, note we use
|
|
* addition instead of *2 since it's easier to optimize
|
|
*/
|
|
r = (mp_word)*tmpt + r + r + (mp_word)u;
|
|
|
|
/* store lower part */
|
|
*tmpt++ = (mp_digit)(r & (mp_word)MP_MASK);
|
|
|
|
/* get carry */
|
|
u = (mp_digit)(r >> (mp_word)DIGIT_BIT);
|
|
}
|
|
/* propagate upwards */
|
|
while (u != 0uL) {
|
|
r = (mp_word)*tmpt + (mp_word)u;
|
|
*tmpt++ = (mp_digit)(r & (mp_word)MP_MASK);
|
|
u = (mp_digit)(r >> (mp_word)DIGIT_BIT);
|
|
}
|
|
}
|
|
|
|
mp_clamp(&t);
|
|
mp_exch(&t, b);
|
|
mp_clear(&t);
|
|
return MP_OKAY;
|
|
}
|
|
#endif
|
|
|
|
/* ref: $Format:%D$ */
|
|
/* git commit: $Format:%H$ */
|
|
/* commit time: $Format:%ai$ */
|