timing_attack.c

   1 #include <stdio.h>
   2 #include <sys/time.h>
   3 #include <time.h>
   4 #include <string.h>
   5
   6
   7 static struct timeval tp1,tp2;
   8
   9 static void start_timer()
  10 {
  11         gettimeofday(&tp1,NULL);
  12 }
  13
  14 static double end_timer()
  15 {
  16         gettimeofday(&tp2,NULL);
  17         return (tp2.tv_sec + (tp2.tv_usec*1.0e-6)) -
  18                 (tp1.tv_sec + (tp1.tv_usec*1.0e-6));
  19 }
  20
  21 static void attack_it(const char *target, int len)
  22 {
  23         int i;
  24         double totals[256];
  25         double this_run[256];
  26         char teststr[len+1];
  27         int c, r, runs, min_c;
  28         double min;
  29
  30         runs = 1000000;
  31
  32
  33         for (i=0;i<len;i++) {
  34                 memset(totals, 0, sizeof(totals));
  35
  36                 for (r=0;r<runs;r++) {
  37                         for (c=0;c<256;c++) {
  38                                 start_timer();
  39                                 teststr[i] = c;
  40                                 memcmp(teststr, target, i+1);
  41                                 this_run[c] = end_timer();
  42                         }
  43                         for (c=0;c<256;c++) {
  44 //                              printf("%3d %lf\n", c, 1000*1000*this_run[c]);
  45                                 totals[c] += this_run[c];
  46                         }
  47                 }
  48
  49                 min_c = 0;
  50                 min = totals[0];
  51                 for (c=1;c<256;c++) {
  52                         if (totals[c] < min) {
  53                                 min = totals[c];
  54                                 min_c = c;
  55                         }
  56                 }
  57                 printf("min_c=%d\n", min_c);
  58         }
  59 }
  60
  61 int main(int argc, char *argv[])
  62 {
  63         attack_it(argv[1], strlen(argv[1]));
  64         return 0;
  65 }