#include #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. * * Tom St Denis, tomstdenis@gmail.com, http://libtom.org */ /* low level squaring, b = a*a, HAC pp.596-597, Algorithm 14.16 */ int s_mp_sqr (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 != ((mp_digit) 0)) { 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 /* \$Source\$ */ /* \$Revision\$ */ /* \$Date\$ */