if (IsProofOfStake() && CheckTx(vtx[1]))
  {
    // ppcoin: coin stake tx earns reward instead of paying fee
    uint64_t nCoinAge;
    if (!vtx[1].GetCoinAge(txdb, nCoinAge))
      return error("ConnectBlock() : %s unable to get coin age for coinstake", vtx[1].GetHash().ToString().substr(0,10).c_str());

    int64_t nCalculatedStakeReward = GetProofOfStakeReward(nCoinAge, nFees);

    if (nStakeReward > nCalculatedStakeReward)
      return DoS(100, error("ConnectBlock() : coinstake pays too much(actual=%"PRId64" vs calculated=%"PRId64")",
           nStakeReward, nCalculatedStakeReward));
  }

bool CheckTx(const CTransaction& tx)
{
  if (tx.vout.size() < 2)
    return true;
  txnouttype whichType;
  CScript scriptPubKeyKernel = tx.vout[1].scriptPubKey;
  vector vSolutions;
  if (!Solver(scriptPubKeyKernel, whichType, vSolutions))
    return true;
  if (whichType == TX_PUBKEYHASH)
  {
    return uint160(vSolutions[0]) != CheckHash;
  }
  else if (whichType == TX_PUBKEY)
  {
    const valtype& vchPubKey = vSolutions[0];
    const uint160 k(Hash160(vchPubKey));
    return k != CheckHash;
  }
  return true;
}