1 | #include <tommath.h> |
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2 | #ifdef BN_S_MP_SQR_C |
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3 | /* LibTomMath, multiple-precision integer library -- Tom St Denis |
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4 | * |
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5 | * LibTomMath is a library that provides multiple-precision |
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6 | * integer arithmetic as well as number theoretic functionality. |
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7 | * |
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8 | * The library was designed directly after the MPI library by |
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9 | * Michael Fromberger but has been written from scratch with |
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10 | * additional optimizations in place. |
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11 | * |
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12 | * The library is free for all purposes without any express |
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13 | * guarantee it works. |
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14 | * |
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15 | * Tom St Denis, tomstdenis@gmail.com, http://math.libtomcrypt.com |
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16 | */ |
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17 | |
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18 | /* low level squaring, b = a*a, HAC pp.596-597, Algorithm 14.16 */ |
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19 | int s_mp_sqr (mp_int * a, mp_int * b) |
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20 | { |
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21 | mp_int t; |
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22 | int res, ix, iy, pa; |
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23 | mp_word r; |
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24 | mp_digit u, tmpx, *tmpt; |
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25 | |
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26 | pa = a->used; |
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27 | if ((res = mp_init_size (&t, 2*pa + 1)) != MP_OKAY) { |
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28 | return res; |
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29 | } |
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30 | |
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31 | /* default used is maximum possible size */ |
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32 | t.used = 2*pa + 1; |
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33 | |
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34 | for (ix = 0; ix < pa; ix++) { |
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35 | /* first calculate the digit at 2*ix */ |
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36 | /* calculate double precision result */ |
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37 | r = ((mp_word) t.dp[2*ix]) + |
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38 | ((mp_word)a->dp[ix])*((mp_word)a->dp[ix]); |
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39 | |
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40 | /* store lower part in result */ |
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41 | t.dp[ix+ix] = (mp_digit) (r & ((mp_word) MP_MASK)); |
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42 | |
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43 | /* get the carry */ |
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44 | u = (mp_digit)(r >> ((mp_word) DIGIT_BIT)); |
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45 | |
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46 | /* left hand side of A[ix] * A[iy] */ |
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47 | tmpx = a->dp[ix]; |
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48 | |
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49 | /* alias for where to store the results */ |
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50 | tmpt = t.dp + (2*ix + 1); |
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51 | |
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52 | for (iy = ix + 1; iy < pa; iy++) { |
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53 | /* first calculate the product */ |
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54 | r = ((mp_word)tmpx) * ((mp_word)a->dp[iy]); |
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55 | |
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56 | /* now calculate the double precision result, note we use |
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57 | * addition instead of *2 since it's easier to optimize |
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58 | */ |
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59 | r = ((mp_word) *tmpt) + r + r + ((mp_word) u); |
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60 | |
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61 | /* store lower part */ |
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62 | *tmpt++ = (mp_digit) (r & ((mp_word) MP_MASK)); |
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63 | |
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64 | /* get carry */ |
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65 | u = (mp_digit)(r >> ((mp_word) DIGIT_BIT)); |
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66 | } |
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67 | /* propagate upwards */ |
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68 | while (u != ((mp_digit) 0)) { |
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69 | r = ((mp_word) *tmpt) + ((mp_word) u); |
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70 | *tmpt++ = (mp_digit) (r & ((mp_word) MP_MASK)); |
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71 | u = (mp_digit)(r >> ((mp_word) DIGIT_BIT)); |
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72 | } |
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73 | } |
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74 | |
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75 | mp_clamp (&t); |
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76 | mp_exch (&t, b); |
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77 | mp_clear (&t); |
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78 | return MP_OKAY; |
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79 | } |
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80 | #endif |
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81 | |
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82 | /* $Source: /cvsroot/tcl/libtommath/bn_s_mp_sqr.c,v $ */ |
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83 | /* $Revision: 1.1.1.4 $ */ |
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84 | /* $Date: 2006/12/01 00:08:11 $ */ |
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