Improved Nonce Construction Scheme for AES CCMP to Evade Initial Counter Prediction

Abstract

IEEE 802.11i standard offers arguably uncompromised confidentiality and integrity services by utilizing advance encryption standard in counter with cipher block chaining message authentication code protocol (AES CCMP). However the Nonce construction mechanism employed in the standard is weak, leading to Initial Counter prediction. Resultantly, the effective Key Length used for encryption is reduced from 128 to 85 bits and Time Memory Trade Off (TMTO) attack becomes a possibility. In this paper, an improved Nonce construction scheme is proposed for the AES CCMP to effectively prevent Initial Counter Prediction and the possibility of a subsequent TMTO attack. The proposed technique involves randomization of the Nonce value to make it unpredictable. The devised technique can be easily employed as a software upgrade in the existing 802.11i based Wireless Local Area Network (WLAN) devices, without any requirement of hardware up gradation.