In this paper, we aim at increasing the strength of weak arbiter physical unclonable function (APUF) which are vulnerable to modeling attacks because of low uniqueness and randomness. We propose a unique technique which takes n × 1 challenge-response pairs (CRPs) from APUF and combines them with ring oscillators (ROs) implemented on the same FPGA to get n × n CRPs. We claim the proposed technique to be immune to modeling attacks to a great extent. The experimental results show that the uniqueness and randomness of the APUF increase by at least 19% and 16%, respectively after the implementation of proposed technique.