With the ever increasing volume of information over wireless medium, securityhas assumed an important dimension. The security of transmitted data over awireless channel aims at protecting the data from unauthorized intrusion.Wireless network security is achieved using cryptographic primitives. Someproperties that give encryption mechanism their cryptographic strength alsomake them very sensitive to channel error as well. Therefore, security for datatransmission over wireless channel results in throughput loss. Trade-offbetween security and throughput is always a major concern in wireless networks.In this paper, a Link Adaptive Encryption scheme is evaluated that adapts tochannel variations and enhances the security level of WLANs without making anycompromise with the network performance. Numerical results obtained throughsimulation are compared with the fixed block length encryption technique in twodifferent modes of operation- Electronic Code Book (ECB) & Cipher BlockChaining (CBC). Optimal block length is also computed, which is assumed to bethe effective strength of the cipher. It has been observed that securityattained with link adaptive scheme operating in ECB mode of cipher is a bettersolution for security and throughput trade-off. However, it is found that ifcomputational security is a major concern, link adaptive scheme in CBC modeshould be preferred.
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