cangrepp

Some cryptographic attacks
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header.c (2988B)

      1 /**
      2  * Precomputer for metaprogramming generated precomputed.h header
      3  * file that is useful.
      4  */
      5 #include <flint.h>
      6 #include <fmpz.h>
      7 #include <stdio.h>
      8 #include <stdlib.h>
      9 
     10 #include <assert.h>
     11 
     12 #define SMALLPRIME_LIMIT (1<<16)
     13 
     14 static slong
     15 calc_len(fmpz_t n)
     16 {
     17   assert(fmpz_cmp_ui(n, 0) > 0);
     18   return (slong) fmpz_size(n);
     19 }
     20 
     21 static void
     22 pparray(FILE* f, const ulong *a, const slong len)
     23 {
     24   slong i;
     25   for(i = 0; i < len; i++) {
     26     if(i == 0) {
     27       fprintf(f, "  ");
     28     } else if(i % 8 == 0) {
     29       fprintf(f, "\n  ");
     30     }
     31     fprintf(f, "0x%016lx, ", a[i]);
     32   }
     33 }
     34 
     35 // ugly, but okay for precomputer
     36 static size_t
     37 count_smallprimes(size_t limit)
     38 {
     39   fmpz_t p;
     40   fmpz_init_set_ui(p, 2);
     41   size_t i = 0;
     42 
     43   while (fmpz_cmp_ui(p, limit) < 0) {
     44     fmpz_nextprime(p, p, 0);
     45     i++;
     46   }  
     47   fmpz_clear(p);
     48 
     49   return i;
     50 }
     51 
     52 static void
     53 print_disclaimer(FILE* f)
     54 {
     55   fprintf(f, "/**\n"
     56 	 " * This file has been automatically computed using the\n"
     57 	 " * precompute/header utility. The purpose is to store\n"
     58 	 " * some constant values, such as\n"
     59 	 " *\n"
     60 	 " * - limbs of a primorial (product of small primes)\n"
     61 	 " * - list of small primes\n"
     62 	 " */\n\n");  
     63 }
     64 
     65 int
     66 main(void)
     67 {
     68   // -= header file =-
     69   
     70   fmpz_t primorial;
     71   fmpz_init(primorial);
     72 
     73   fmpz_primorial(primorial, 1 << 16);
     74 
     75   slong len = calc_len(primorial);
     76   ulong *out = malloc(len * sizeof(*out));
     77 
     78   fmpz_get_ui_array(out, len, primorial);
     79 
     80   FILE* header = fopen("/tmp/precomputed.h", "w");
     81   fprintf(header, "//  --------------- precomputed.h ---------------------\n");
     82   fprintf(header, "#ifndef PRECOMPUTED_H\n"
     83 	 "#define PRECOMPUTED_H\n\n");
     84   print_disclaimer(header);
     85   fprintf(header, "#include <flint.h>\n\n");
     86   
     87   fprintf(header, "#define PC_PRIMORIAL_UI_ARRAY_LEN %ld\n", len);
     88   fprintf(header, "#define PC_SMALLPRIMES_LEN %ld\n\n",
     89 	 count_smallprimes(SMALLPRIME_LIMIT));
     90   fprintf(header, "extern const ulong "
     91 	 "pc_primorial_ui_array[PC_PRIMORIAL_UI_ARRAY_LEN];\n"
     92 	 "extern const ulong "
     93 	 "pc_smallprimes[PC_SMALLPRIMES_LEN];\n"
     94 	 "#endif\n\n");
     95   fclose(header);
     96   
     97   // -= source file =-
     98 
     99   FILE* source = fopen("/tmp/precomputed.c", "w");
    100   fprintf(source, "// ------------- precomputed.c ------------------------\n");
    101 
    102   print_disclaimer(source);
    103   fprintf(source, "#include \"precomputed.h\"\n");
    104   fprintf(source, "const ulong "
    105 	 "pc_primorial_ui_array[PC_PRIMORIAL_UI_ARRAY_LEN] = {\n");
    106   pparray(source, out, len);
    107   fprintf(source, "};\n\n");
    108 
    109   fmpz_clear(primorial);
    110   free(out);
    111 
    112   // -= small primes =-
    113 
    114   fmpz_t p;
    115   fmpz_init_set_ui(p, 2);
    116   size_t i = 0;
    117 
    118   fprintf(source, "const ulong pc_smallprimes[PC_SMALLPRIMES_LEN] = {\n");
    119   while (fmpz_cmp_ui(p, (1 << 16)) < 0) {
    120     if (i == 0) {
    121       fprintf(source, "  ");
    122     } else if (i % 8 == 0) {
    123       fprintf(source, "\n  ");
    124     }
    125 
    126     fmpz_fprint(source, p);
    127     fprintf(source, ", ");
    128 
    129     fmpz_nextprime(p, p, 0);
    130     
    131     i++;
    132   }
    133   fprintf(source, "};\n\n");
    134 
    135   fclose(source);
    136   fmpz_clear(p);
    137   
    138   return 0;
    139 }