IEEE 802.11i [21], an IEEE standard ratified June 24,
2004, is designed to provide enhanced security in the
Medium Access Control (MAC) layer for 802.11
networks. The 802.11i specification defines two classes of
security algorithms: Robust Security Network Association
(RSNA), and Pre-RSNA. Pre-RSNA security consists of
Wired Equivalent Privacy (WEP) and 802.11 entityauthentication. RSNA provides two data confidentiality
protocols, called the Temporal Key Integrity Protocol
(TKIP) and the Counter-mode/CBC-MAC Protocol
(CCMP), and the RSNA establishment procedure,
including 802.1X authentication and key management
protocols.
This paper analyzes security aspects of the 802.11i
specification, considering data confidentiality, integrity,
mutual authentication, and availability. Our analysis
suggests that 802.11i is a well-designed standard for data
confidentiality, integrity, and mutual authentication,
promising to improve the security of wireless networks.
At the same time, some vexing Denial-of-Service (DoS)
attacks remain. We review the known DoS attacks and
describe appropriate countermeasures. We also describe
two new DoS attacks – RSN Information Element (RSN
IE) Poisoning and 4-Way Handshake Blocking – and
present countermeasures for these. We also analyze the
failure-recovery strategy in 802.11i and discuss associated
tradeoffs. Finally we outline an improved version of
802.11i that addresses all the vulnerabilities discussed in
this paper.