-rw-r--r-- 570 cryptattacktester-20231020/bruteforce2_prob.cpp raw
#include <cassert>
#include "bruteforce2_prob.h"

using namespace std;

bigfloat bruteforce2_prob(const vector<bigint> &params,const vector<bigint> &attackparams)
{
  bigint n = params.at(0);
  bigint k = params.at(1);
  bigint w = params.at(2);
  bigint iters = attackparams.at(0);
  bigint successes = 0;
  for (bigint v = 0;v <= w;++v) {
    bigint binkv = binomial(k,v);
    iters -= binkv;
    successes += binkv*binomial(n-k,w-v);
    assert(iters >= 0);
    if (iters == 0) break;
  }
  assert(iters == 0);
  return bigfloat(successes)/bigfloat(binomial(n,w));
}