I. Introduction
AT the time of this writing, the Internet is typically accessed through the wireless infrastructure (e.g., cellular networks and Wi-Fi) [1]. Consequently, the security of wireless communications plays an increasingly important role in the cybercrime defense against unauthorized activities. Moreover, due to the broadcast nature of the wireless medium, transmissions between legitimate users may be readily overheard and intercepted by unauthorized parties, which makes wireless transmission vulnerable to potential eavesdropping attacks. As a result, wireless security has received growing research attention in recent years. In existing wireless communication systems, cryptographic techniques are used for preventing an unauthorized eavesdropper from intercepting message transmissions between legitimate users [2], [3]. Although the cryptographic methods indeed improve the communication security, this comes at the expense of increased communication and computational overheads. To be specific, the increased complexity of encryption algorithm enhances the security level of wireless communications, which, unfortunately, requires more processing resources for encryption and decryption and increases latency imposed. Furthermore, the encryption introduces additional redundancy and, hence, results in an increased overhead. Additionally, the encryption may be still decrypted by an eavesdropper using an exhaustive key search (also known as brute-force attack).