Mercurial > dropbear
annotate bn_s_mp_sqr.c @ 190:d8254fc979e9 libtommath-orig LTM_0.35
Initial import of libtommath 0.35
| author | Matt Johnston <matt@ucc.asn.au> |
|---|---|
| date | Fri, 06 May 2005 08:59:30 +0000 |
| parents | d29b64170cf0 |
| children |
| rev | line source |
|---|---|
| 142 | 1 #include <tommath.h> |
| 2 #ifdef BN_S_MP_SQR_C | |
| 2 | 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, [email protected], http://math.libtomcrypt.org | |
| 16 */ | |
| 17 | |
| 18 /* low level squaring, b = a*a, HAC pp.596-597, Algorithm 14.16 */ | |
|
190
d8254fc979e9
Initial import of libtommath 0.35
Matt Johnston <matt@ucc.asn.au>
parents:
142
diff
changeset
|
19 int s_mp_sqr (mp_int * a, mp_int * b) |
| 2 | 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 } | |
| 142 | 80 #endif |