crypto/bn/old/bn_high.c

   1 #include <stdio.h>
   2 #include "cryptlib.h"
   3 #include "bn_lcl.h"
   4
   5 #undef BN_MUL_HIGH_DEBUG
   6
   7 #ifdef BN_MUL_HIGH_DEBUG
   8 #define debug_BN_print(a,b,c) BN_print_fp(a,b); printf(c);
   9 #else
  10 #define debug_BN_print(a,b,c)
  11 #endif
  12
  13 int BN_mul_high(BIGNUM *r,BIGNUM *a,BIGNUM *b,BIGNUM *low, int words);
  14
  15 #undef t1
  16 #undef t2
  17
  18 int BN_mul_high(BIGNUM *r, BIGNUM *a, BIGNUM *b, BIGNUM *low, int words)
  19         {
  20         int w2,borrow=0,full=0;
  21         BIGNUM t1,t2,t3,h,ah,al,bh,bl,m,s0,s1;
  22         BN_ULONG ul1,ul2;
  23
  24         BN_mul(r,a,b);
  25         BN_rshift(r,r,words*BN_BITS2);
  26         return(1);
  27
  28         w2=(words+1)/2;
  29
  30 #ifdef BN_MUL_HIGH_DEBUG
  31 fprintf(stdout,"words=%d w2=%d\n",words,w2);
  32 #endif
  33 debug_BN_print(stdout,a," a\n");
  34 debug_BN_print(stdout,b," b\n");
  35 debug_BN_print(stdout,low," low\n");
  36         BN_init(&al); BN_init(&ah);
  37         BN_init(&bl); BN_init(&bh);
  38         BN_init(&t1); BN_init(&t2); BN_init(&t3);
  39         BN_init(&s0); BN_init(&s1);
  40         BN_init(&h); BN_init(&m);
  41
  42         bn_set_low (&al,a,w2);
  43         bn_set_high(&ah,a,w2);
  44         bn_set_low (&bl,b,w2);
  45         bn_set_high(&bh,b,w2);
  46
  47         bn_set_low(&s0,low,w2);
  48         bn_set_high(&s1,low,w2);
  49
  50 debug_BN_print(stdout,&al," al\n");
  51 debug_BN_print(stdout,&ah," ah\n");
  52 debug_BN_print(stdout,&bl," bl\n");
  53 debug_BN_print(stdout,&bh," bh\n");
  54 debug_BN_print(stdout,&s0," s0\n");
  55 debug_BN_print(stdout,&s1," s1\n");
  56
  57         /* Calculate (al-ah)*(bh-bl) */
  58         BN_sub(&t1,&al,&ah);
  59         BN_sub(&t2,&bh,&bl);
  60         BN_mul(&m,&t1,&t2);
  61
  62         /* Calculate ah*bh */
  63         BN_mul(&h,&ah,&bh);
  64
  65         /* s0 == low(al*bl)
  66          * s1 == low(ah*bh)+low((al-ah)*(bh-bl))+low(al*bl)+high(al*bl)
  67          * We know s0 and s1 so the only unknown is high(al*bl)
  68          * high(al*bl) == s1 - low(ah*bh+(al-ah)*(bh-bl)+s0)
  69          */
  70         BN_add(&m,&m,&h);
  71         BN_add(&t2,&m,&s0);
  72
  73 debug_BN_print(stdout,&t2," middle value\n");
  74
  75         /* Quick and dirty mask off of high words */
  76         if (w2 < t2.top) t2.top=w2;
  77 #if 0
  78         bn_set_low(&t3,&t2,w2);
  79 #endif
  80
  81 debug_BN_print(stdout,&t2," low middle value\n");
  82         BN_sub(&t1,&s1,&t2);
  83
  84         if (t1.neg)
  85                 {
  86 debug_BN_print(stdout,&t1," before\n");
  87                 BN_zero(&t2);
  88                 BN_set_bit(&t2,w2*BN_BITS2);
  89                 BN_add(&t1,&t2,&t1);
  90                 /* BN_mask_bits(&t1,w2*BN_BITS2); */
  91                 /* if (words < t1.top) t1.top=words; */
  92 debug_BN_print(stdout,&t1," after\n");
  93                 borrow=1;
  94                 }
  95
  96 /* XXXXX SPEED THIS UP */
  97         /* al*bl == high(al*bl)<<words+s0 */
  98         BN_lshift(&t1,&t1,w2*BN_BITS2);
  99         BN_add(&t1,&t1,&s0);
 100         if (w2*2 < t1.top) t1.top=w2*2; /* This should not happen? */
 101
 102         /* We now have
 103          * al*bl                        - t1
 104          * (al-ah)*(bh-bl)+ah*bh        - m
 105          * ah*bh                        - h
 106          */
 107 #if 0
 108         BN_add(&m,&m,&t1);
 109 debug_BN_print(stdout,&t1," s10\n");
 110 debug_BN_print(stdout,&m," s21\n");
 111 debug_BN_print(stdout,&h," s32\n");
 112         BN_lshift(&m,&m,w2*BN_BITS2);
 113         BN_lshift(&h,&h,w2*2*BN_BITS2);
 114         BN_add(r,&m,&t1);
 115         BN_add(r,r,&h);
 116         BN_rshift(r,r,w2*2*BN_BITS2);
 117 #else
 118         BN_add(&m,&m,&t1);              /* Do a cmp then +1 if needed? */
 119         bn_set_high(&t3,&t1,w2);
 120         BN_add(&m,&m,&t3);
 121         bn_set_high(&t3,&m,w2);
 122         BN_add(r,&h,&t3);
 123 #endif
 124
 125 #ifdef BN_MUL_HIGH_DEBUG
 126 printf("carry=%d\n",borrow);
 127 #endif
 128 debug_BN_print(stdout,r," ret\n");
 129         BN_free(&t1); BN_free(&t2);
 130         BN_free(&m); BN_free(&h);
 131         return(1);
 132         }
 133
 134
 135