RC4 is one of the most widely used stream cipher due to its simplicity, speed and efficiency. In this paper we have presented a chronological survey of RC4 stream cipher demonstrating its weaknesses followed by the various RC4 enhancements from the literature. From the recently observed cryptanalytic attempts on RC4 it is established that innovative research efforts are required to develop secure RC4 algorithm, which can remove the weaknesses of RC4, such as biased bytes, key collisions, and key recovery attacks specifically on WEP and WPA. These flaws in RC4 are offering open challenge for developers. Hence our chronological survey corroborates the fact that even though researchers are working on RC4 stream cipher since last two decades, it still offers a plethora of research issues related to statistical weaknesses in either state or keystream.

With the ever increasing volume of information over wireless medium, security has assumed an important dimension. The security of transmitted data over a wireless channel aims at protecting the data from unauthorized intrusion. Wireless network security is achieved using cryptographic primitives. Some properties that give encryption mechanism their cryptographic strength also make them very sensitive to channel error as well. Therefore, security for data transmission over wireless channel results in throughput loss. Tradeoff between security and throughput is always a major concern in wireless networks. In this paper, a Link Adaptive Encryption scheme is evaluated that adapts to channel variations and enhances the security level of WLANs without making any compromise with the network performance. Numerical results obtained through simulation for link adaptive encryption scheme are compared with the fixed block length encryption technique operating in Cipher Block Chaining (CBC) mode of operation. Optimal block length is also computed, which is assumed to be the effective strength of the cipher. It has been observed that security attained with link adaptive scheme operating in CBC mode is a better solution for security and throughput tradeoff.