Method: RFuzz::FuzzRnd#initialize

Defined in:
ext/fuzzrnd/fuzzrnd.c

#seed ⇒ Object

Seeds the global ArcFour random generator with the given seed. The same seeds should produce the exact same stream of random data so that you can get large amounts of randomness but replay possible interactions using just an initial key.

This function also doubles as the FuzzRnd.initialize method since they do nearly the same thing.

Taken from www.mozilla.org/projects/security/pki/nss/draft-kaukonen-cipher-arcfour-03.txt sample code, but compared with the output of the ArcFour implementation in the Phelix test code to make sure it is the same initialization. The main difference is that this init takes an arbitrary keysize while the original Phelix ArcFour only took a 32bit key.

Returns itself so you can seed and then get data easily.



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# File 'ext/fuzzrnd/fuzzrnd.c', line 99

VALUE FuzzRnd_seed(VALUE self, VALUE data) {

  unsigned int t, u;
  unsigned int keyindex;
  unsigned int stateindex;
  unsigned char *state;
  unsigned int counter;
  char *key = NULL;
  size_t key_len = 0;

  REQUIRE_TYPE(data, T_STRING);

  key = RSTRING(data)->ptr;
  key_len = RSTRING(data)->len;

  state = ArcFour.sbox;
  ArcFour.i = 0;
  ArcFour.j = 0;

  for (counter = 0; counter < 256; counter++)
    state[counter] = counter;

  keyindex = 0;
  stateindex = 0;
  for (counter = 0; counter < 256; counter++)
  {
    t = state[counter];
    stateindex = (stateindex + key[keyindex] + t) & 0xff;
    u = state[stateindex];
    state[stateindex] = t;
    state[counter] = u;
    if (++keyindex >= key_len)
      keyindex = 0;
  }

  return self;
}