private SecureUtils.K2Output getK2Output(final Message message) {
        final NetworkKey networkKey;
        if (message.getAkf() == APPLICATION_KEY_IDENTIFIER) {
            networkKey = mNetworkLayerCallbacks.getPrimaryNetworkKey();
        } else {
            final int netKeyIndex = message.getApplicationKey().getBoundNetKeyIndex();
            networkKey = mNetworkLayerCallbacks.getNetworkKey(netKeyIndex);
        }
        return networkKey.getTxDerivatives();
    }
Returns the master credentials {@link SecureUtils.K2Output}

@param message Message
mesh/src/main/java/no/nordicsemi/android/mesh/transport/NetworkLayer.java