## File: bn_s_mp_sqr.c

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libtommath 1.1.0-3
 `123456789101112131415161718192021222324252627282930313233343536373839404142434445464748495051525354555657585960616263646566676869707172737475767778798081` ``````#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. * * SPDX-License-Identifier: Unlicense */ /* 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: HEAD -> master, tag: v1.1.0 */ /* git commit: 08549ad6bc8b0cede0b357a9c341c5c6473a9c55 */ /* commit time: 2019-01-28 20:32:32 +0100 */ ``````