release/src/router/dropbear/libtommath/bn_mp_toom_sqr.c

   1 #include <tommath.h>
   2 #ifdef BN_MP_TOOM_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@gmail.com, http://math.libtomcrypt.com
  16  */
  17
  18 /* squaring using Toom-Cook 3-way algorithm */
  19 int
  20 mp_toom_sqr(mp_int *a, mp_int *b)
  21 {
  22     mp_int w0, w1, w2, w3, w4, tmp1, a0, a1, a2;
  23     int res, B;
  24
  25     /* init temps */
  26     if ((res = mp_init_multi(&w0, &w1, &w2, &w3, &w4, &a0, &a1, &a2, &tmp1, NULL)) != MP_OKAY) {
  27        return res;
  28     }
  29
  30     /* B */
  31     B = a->used / 3;
  32
  33     /* a = a2 * B**2 + a1 * B + a0 */
  34     if ((res = mp_mod_2d(a, DIGIT_BIT * B, &a0)) != MP_OKAY) {
  35        goto ERR;
  36     }
  37
  38     if ((res = mp_copy(a, &a1)) != MP_OKAY) {
  39        goto ERR;
  40     }
  41     mp_rshd(&a1, B);
  42     mp_mod_2d(&a1, DIGIT_BIT * B, &a1);
  43
  44     if ((res = mp_copy(a, &a2)) != MP_OKAY) {
  45        goto ERR;
  46     }
  47     mp_rshd(&a2, B*2);
  48
  49     /* w0 = a0*a0 */
  50     if ((res = mp_sqr(&a0, &w0)) != MP_OKAY) {
  51        goto ERR;
  52     }
  53
  54     /* w4 = a2 * a2 */
  55     if ((res = mp_sqr(&a2, &w4)) != MP_OKAY) {
  56        goto ERR;
  57     }
  58
  59     /* w1 = (a2 + 2(a1 + 2a0))**2 */
  60     if ((res = mp_mul_2(&a0, &tmp1)) != MP_OKAY) {
  61        goto ERR;
  62     }
  63     if ((res = mp_add(&tmp1, &a1, &tmp1)) != MP_OKAY) {
  64        goto ERR;
  65     }
  66     if ((res = mp_mul_2(&tmp1, &tmp1)) != MP_OKAY) {
  67        goto ERR;
  68     }
  69     if ((res = mp_add(&tmp1, &a2, &tmp1)) != MP_OKAY) {
  70        goto ERR;
  71     }
  72
  73     if ((res = mp_sqr(&tmp1, &w1)) != MP_OKAY) {
  74        goto ERR;
  75     }
  76
  77     /* w3 = (a0 + 2(a1 + 2a2))**2 */
  78     if ((res = mp_mul_2(&a2, &tmp1)) != MP_OKAY) {
  79        goto ERR;
  80     }
  81     if ((res = mp_add(&tmp1, &a1, &tmp1)) != MP_OKAY) {
  82        goto ERR;
  83     }
  84     if ((res = mp_mul_2(&tmp1, &tmp1)) != MP_OKAY) {
  85        goto ERR;
  86     }
  87     if ((res = mp_add(&tmp1, &a0, &tmp1)) != MP_OKAY) {
  88        goto ERR;
  89     }
  90
  91     if ((res = mp_sqr(&tmp1, &w3)) != MP_OKAY) {
  92        goto ERR;
  93     }
  94
  95
  96     /* w2 = (a2 + a1 + a0)**2 */
  97     if ((res = mp_add(&a2, &a1, &tmp1)) != MP_OKAY) {
  98        goto ERR;
  99     }
 100     if ((res = mp_add(&tmp1, &a0, &tmp1)) != MP_OKAY) {
 101        goto ERR;
 102     }
 103     if ((res = mp_sqr(&tmp1, &w2)) != MP_OKAY) {
 104        goto ERR;
 105     }
 106
 107     /* now solve the matrix
 108
 109        0  0  0  0  1
 110        1  2  4  8  16
 111        1  1  1  1  1
 112        16 8  4  2  1
 113        1  0  0  0  0
 114
 115        using 12 subtractions, 4 shifts, 2 small divisions and 1 small multiplication.
 116      */
 117
 118      /* r1 - r4 */
 119      if ((res = mp_sub(&w1, &w4, &w1)) != MP_OKAY) {
 120         goto ERR;
 121      }
 122      /* r3 - r0 */
 123      if ((res = mp_sub(&w3, &w0, &w3)) != MP_OKAY) {
 124         goto ERR;
 125      }
 126      /* r1/2 */
 127      if ((res = mp_div_2(&w1, &w1)) != MP_OKAY) {
 128         goto ERR;
 129      }
 130      /* r3/2 */
 131      if ((res = mp_div_2(&w3, &w3)) != MP_OKAY) {
 132         goto ERR;
 133      }
 134      /* r2 - r0 - r4 */
 135      if ((res = mp_sub(&w2, &w0, &w2)) != MP_OKAY) {
 136         goto ERR;
 137      }
 138      if ((res = mp_sub(&w2, &w4, &w2)) != MP_OKAY) {
 139         goto ERR;
 140      }
 141      /* r1 - r2 */
 142      if ((res = mp_sub(&w1, &w2, &w1)) != MP_OKAY) {
 143         goto ERR;
 144      }
 145      /* r3 - r2 */
 146      if ((res = mp_sub(&w3, &w2, &w3)) != MP_OKAY) {
 147         goto ERR;
 148      }
 149      /* r1 - 8r0 */
 150      if ((res = mp_mul_2d(&w0, 3, &tmp1)) != MP_OKAY) {
 151         goto ERR;
 152      }
 153      if ((res = mp_sub(&w1, &tmp1, &w1)) != MP_OKAY) {
 154         goto ERR;
 155      }
 156      /* r3 - 8r4 */
 157      if ((res = mp_mul_2d(&w4, 3, &tmp1)) != MP_OKAY) {
 158         goto ERR;
 159      }
 160      if ((res = mp_sub(&w3, &tmp1, &w3)) != MP_OKAY) {
 161         goto ERR;
 162      }
 163      /* 3r2 - r1 - r3 */
 164      if ((res = mp_mul_d(&w2, 3, &w2)) != MP_OKAY) {
 165         goto ERR;
 166      }
 167      if ((res = mp_sub(&w2, &w1, &w2)) != MP_OKAY) {
 168         goto ERR;
 169      }
 170      if ((res = mp_sub(&w2, &w3, &w2)) != MP_OKAY) {
 171         goto ERR;
 172      }
 173      /* r1 - r2 */
 174      if ((res = mp_sub(&w1, &w2, &w1)) != MP_OKAY) {
 175         goto ERR;
 176      }
 177      /* r3 - r2 */
 178      if ((res = mp_sub(&w3, &w2, &w3)) != MP_OKAY) {
 179         goto ERR;
 180      }
 181      /* r1/3 */
 182      if ((res = mp_div_3(&w1, &w1, NULL)) != MP_OKAY) {
 183         goto ERR;
 184      }
 185      /* r3/3 */
 186      if ((res = mp_div_3(&w3, &w3, NULL)) != MP_OKAY) {
 187         goto ERR;
 188      }
 189
 190      /* at this point shift W[n] by B*n */
 191      if ((res = mp_lshd(&w1, 1*B)) != MP_OKAY) {
 192         goto ERR;
 193      }
 194      if ((res = mp_lshd(&w2, 2*B)) != MP_OKAY) {
 195         goto ERR;
 196      }
 197      if ((res = mp_lshd(&w3, 3*B)) != MP_OKAY) {
 198         goto ERR;
 199      }
 200      if ((res = mp_lshd(&w4, 4*B)) != MP_OKAY) {
 201         goto ERR;
 202      }
 203
 204      if ((res = mp_add(&w0, &w1, b)) != MP_OKAY) {
 205         goto ERR;
 206      }
 207      if ((res = mp_add(&w2, &w3, &tmp1)) != MP_OKAY) {
 208         goto ERR;
 209      }
 210      if ((res = mp_add(&w4, &tmp1, &tmp1)) != MP_OKAY) {
 211         goto ERR;
 212      }
 213      if ((res = mp_add(&tmp1, b, b)) != MP_OKAY) {
 214         goto ERR;
 215      }
 216
 217 ERR:
 218      mp_clear_multi(&w0, &w1, &w2, &w3, &w4, &a0, &a1, &a2, &tmp1, NULL);
 219      return res;
 220 }
 221
 222 #endif
 223
 224 /* $Source: /cvs/libtom/libtommath/bn_mp_toom_sqr.c,v $ */
 225 /* $Revision: 1.3 $ */
 226 /* $Date: 2006/03/31 14:18:44 $ */