// the same EC parameters
ECKeyPairGenerator keyGen = new ECKeyPairGenerator();
keyGen.init(new ECKeyGenerationParameters(privKey.getParameters(), this.random));
tempPair = keyGen.generateKeyPair();
// BigInteger Vx = tempPair.getPublic().getW().getAffineX();
ECPublicKeyParameters V = (ECPublicKeyParameters)tempPair.getPublic(); // get temp's public key
BigInteger Vx = V.getQ().getX().toBigInteger(); // get the point's x coordinate