1 #include <tommath.h> 2 #ifdef BN_S_MP_SQR_C 3 /* LibTomMath, multiple-precision integer library -- Tom St Denis 4 * 5 * LibTomMath is a library that provides multiple-precision 6 * integer arithmetic as well as number theoretic functionality. 7 * 8 * The library was designed directly after the MPI library by 9 * Michael Fromberger but has been written from scratch with 10 * additional optimizations in place. 11 * 12 * The library is free for all purposes without any express 13 * guarantee it works. 14 * 15 * Tom St Denis, tomstdenis (at) gmail.com, http://math.libtomcrypt.com 16 */ 17 18 /* low level squaring, b = a*a, HAC pp.596-597, Algorithm 14.16 */ 19 int s_mp_sqr (mp_int * a, mp_int * b) 20 { 21 mp_int t; 22 int res, ix, iy, pa; 23 mp_word r; 24 mp_digit u, tmpx, *tmpt; 25 26 pa = a->used; 27 if ((res = mp_init_size (&t, 2*pa + 1)) != MP_OKAY) { 28 return res; 29 } 30 31 /* default used is maximum possible size */ 32 t.used = 2*pa + 1; 33 34 for (ix = 0; ix < pa; ix++) { 35 /* first calculate the digit at 2*ix */ 36 /* calculate double precision result */ 37 r = ((mp_word) t.dp[2*ix]) + 38 ((mp_word)a->dp[ix])*((mp_word)a->dp[ix]); 39 40 /* store lower part in result */ 41 t.dp[ix+ix] = (mp_digit) (r & ((mp_word) MP_MASK)); 42 43 /* get the carry */ 44 u = (mp_digit)(r >> ((mp_word) DIGIT_BIT)); 45 46 /* left hand side of A[ix] * A[iy] */ 47 tmpx = a->dp[ix]; 48 49 /* alias for where to store the results */ 50 tmpt = t.dp + (2*ix + 1); 51 52 for (iy = ix + 1; iy < pa; iy++) { 53 /* first calculate the product */ 54 r = ((mp_word)tmpx) * ((mp_word)a->dp[iy]); 55 56 /* now calculate the double precision result, note we use 57 * addition instead of *2 since it's easier to optimize 58 */ 59 r = ((mp_word) *tmpt) + r + r + ((mp_word) u); 60 61 /* store lower part */ 62 *tmpt++ = (mp_digit) (r & ((mp_word) MP_MASK)); 63 64 /* get carry */ 65 u = (mp_digit)(r >> ((mp_word) DIGIT_BIT)); 66 } 67 /* propagate upwards */ 68 while (u != ((mp_digit) 0)) { 69 r = ((mp_word) *tmpt) + ((mp_word) u); 70 *tmpt++ = (mp_digit) (r & ((mp_word) MP_MASK)); 71 u = (mp_digit)(r >> ((mp_word) DIGIT_BIT)); 72 } 73 } 74 75 mp_clamp (&t); 76 mp_exch (&t, b); 77 mp_clear (&t); 78 return MP_OKAY; 79 } 80 #endif 81 82 /* $Source: /cvs/libtom/libtommath/bn_s_mp_sqr.c,v $ */ 83 /* $Revision: 1.3 $ */ 84 /* $Date: 2006/03/31 14:18:44 $ */ 85
