src/Rand.h

   1 #ifndef RAND_H
   2 #define RAND_H
   3
   4 #include <gmpxx.h>
   5
   6 /**
   7  * All random functions uses "/dev/urandom".
   8  */
   9 class Rand
  10 {
  11 public:
  12    /**
  13      * Returns a random number with a maximum size of 'sizeBits'.
  14      * If 'forceSize' is true the size is exactly 'sizeBits', so the highest bit will always be 1.
  15      *
  16      * For example, for 'sizeBits' = 12 and 'forceSize' = true, the returned number will be in the following range:
  17      *   [2^11, 2^12-1]
  18      *
  19      * For 'sizeBits' = 12 and 'forceSize' = false, the returned number will be in the following range:
  20      *   [0, 2^12-1]
  21      */
  22    static mpz_class randSize(int sizeBits, bool forceSize = true);
  23
  24    /**
  25      * Return a random number n such as:
  26      *    'from' <= n <= 'to'
  27      */
  28    static mpz_class randLimits(const mpz_class& from, const mpz_class& to);
  29
  30    static mpz_class randPrime(const int size_bits);
  31
  32 private:
  33    /**
  34      * Read a rand from "/dev/urandom" of size 'size' in byte to the given array 'to'.
  35      */
  36    static void readRand(char* to, int size);
  37 };
  38
  39 #endif