byte[] getClientChallenge2() {
            if (clientChallenge2 == null) {
                clientChallenge2 = makeRandomChallenge(random);
            }
            return clientChallenge2;
        }
Calculate and return second client challenge
httpclient5/src/main/java/org/apache/hc/client5/http/impl/auth/NTLMEngineImpl.java