src/Rand.h

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