Imperfect Counter Mode Utilization - IEEE 802.11i Wireless LAN

M.J. Hussain, M.U. Mufti, and U. Ilyas (Pakistan)


Wireless Networks standards and protocols, Encryption and Cryptography, Computer security, IEEE 802.11i.


Counter Mode has recently been employed to provide data confidentiality to IEEE 802.11i wireless LANs. It is found that CCMP has been designed with a weak nonce construction and transmission mechanism, which leads to the exposure of initial counter value. This weak construction of nonce renders the protocol vulnerable to attacks by intruders. This paper presents how the initial counter can be pre-computed by the intruder. This vulnerability of counter block value leads to pre computation attack on the counter mode encryption of CCMP. The failure of the counter mode will result in the collapse of the whole security mechanism of 802.11 WLAN. An unpredictable PN field is recommended to be used to encounter the possible pre-computation attack.

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