The intrinsic broadcast nature of wireless communication let the attackers to initiate several passive attacks such as eavesdropping. In this attack, the attackers do not disturb/stop or interrupt the communication channel, but it will silently steal the information between authentic users. For this purpose, physical layer security (PLS) is one of the promising methodologies to secure wireless transmissions from eavesdroppers. However, PLS is further divided into keyless security and secret key‐based security. The keyless security is not practically implemented because it requires full/part of instantaneous/statistical channel state information (CSI) of the eavesdroppers. Alternatively, key‐based security is exploiting the randomness and reciprocity of wireless channels that do not require any CSI from an eavesdropper. The secret key‐based security is due to the unpredictability of wireless channels between two users. However, the secret key‐based security mainly on two basic parameters, i.e. coherence time and transmission power. Nevertheless, the wireless channel between users has a short coherence time, and it will provide shorter keys' length due to which eavesdropper can easily extract keys between communicating parties. To overcome this limitation, we proposed the power allocation scheme to improve the secret key generation rate (SKGR) to strengthen the security between authentic users.