How to use

getQ

method

in

org.spongycastle.crypto.params.DHParameters

  public int hashCode()
  {
    return getP().hashCode() ^ getG().hashCode() ^ (getQ() != null ? getQ().hashCode() : 0);
  }
}

public static boolean areCompatibleParameters(DHParameters a, DHParameters b)
{
  return a.getP().equals(b.getP()) && a.getG().equals(b.getG())
    && (a.getQ() == null || b.getQ() == null || a.getQ().equals(b.getQ()));
}

  public int hashCode()
  {
    return getP().hashCode() ^ getG().hashCode() ^ (getQ() != null ? getQ().hashCode() : 0);
  }
}

public boolean equals(
  Object  obj)
{
  if (!(obj instanceof DHParameters))
  {
    return false;
  }
  DHParameters    pm = (DHParameters)obj;
  if (this.getQ() != null)
  {
    if (!this.getQ().equals(pm.getQ()))
    {
      return false;
    }
  }
  else
  {
    if (pm.getQ() != null)
    {
      return false;
    }
  }
  return pm.getP().equals(p) && pm.getG().equals(g);
}

public boolean equals(
  Object  obj)
{
  if (!(obj instanceof DHParameters))
  {
    return false;
  }
  DHParameters    pm = (DHParameters)obj;
  if (this.getQ() != null)
  {
    if (!this.getQ().equals(pm.getQ()))
    {
      return false;
    }
  }
  else
  {
    if (pm.getQ() != null)
    {
      return false;
    }
  }
  return pm.getP().equals(p) && pm.getG().equals(g);
}

private BigInteger validate(BigInteger y, DHParameters dhParams)
{
  if (y == null)
  {
    throw new NullPointerException("y value cannot be null");
  }
  // TLS check
  if (y.compareTo(TWO) < 0 || y.compareTo(dhParams.getP().subtract(TWO)) > 0)
  {
    throw new IllegalArgumentException("invalid DH public key");
  }
  if (dhParams.getQ() != null)
  {
    if (ONE.equals(y.modPow(dhParams.getQ(), dhParams.getP())))
    {
      return y;
    }
    throw new IllegalArgumentException("Y value does not appear to be in correct group");
  }
  else
  {
    return y;         // we can't validate without Q.
  }
}

BigInteger xInverse = x.modInverse(DH_GROUP_PARAMETERS.getQ());
BigInteger i = iDoubleBlind.modPow(xInverse, DH_GROUP_PARAMETERS.getP());

BigInteger calculatePrivate(DHParameters dhParams, SecureRandom random)
{
  BigInteger p = dhParams.getP();
  int limit = dhParams.getL();
  if (limit != 0)
  {
    return new BigInteger(limit, random).setBit(limit - 1);
  }
  BigInteger min = TWO;
  int m = dhParams.getM();
  if (m != 0)
  {
    min = ONE.shiftLeft(m - 1);
  }
  BigInteger max = p.subtract(TWO);
  BigInteger q = dhParams.getQ();
  if (q != null)
  {
    max = q.subtract(TWO);
  }
  return BigIntegers.createRandomInRange(min, max, random);
}

BigInteger q = dhParams.getQ();
if (q == null)