This work is motivated by the fact that the secret key generation and refreshment of the key at the physical layer, based on randomness from reciprocity in the wireless channel, is challenged by little variations in the channel, particularly in an indoor environment. We propose a new technique, AnaMPhy, which uses multi-fold anonymity to refresh key at a high rate at two participating transceivers. The key generation and agreement in AnaMPhy is functional in challenging environments with very low or no variations in wireless channels. The idea is to hide the identity of the transmitter and the receiver, using medium access control (MAC) and physical layer strategies (randomization in oscillator drift), and use pulse amplitude modulation (PAM) symbols to confuse and adversary. The secret key is the function of the message's source, chosen symbols and the channel's state. In doing so, confusion at the adversary increases manifold and Alice and Bob are able to refresh their secrets whenever needed. The proposed method is also implemented on software-defined radio (SDR). We argue that key refreshment using low complexity secret refreshment of AnaMPhy would be critical for decentralized systems in IoT and cyber physical systems (CPS) networks.