WPA Passive Dictionary Attack Overview | WPA Passive Dictionary Attack Overview TakehiroTakahashi This short paper presents an attack against the Pre-Shared Key version of the WPA encryption platform and argues the need for replacement. What is WPA The WPA standard is a subset of the wireless security standard intended to address the cryptographic shortcomings of Wired Equivalent Protocol WEP . WPA comes in two forms per-user based security designed for enterprises and a pre-shared key mode designed for consumers. While the former utilizes a RADIUS server to ensure per user keying the latter greatly simplifies deployment for home and SOHO users by having a master key based on a pass phrase for the wireless LAN. WPA and are necessary because WEP has known weaknesses poor key manageability and lacks simplicity needed among home users for deployment. Types of WPA Enterprise Mode - Per-user authentication based protocol with the combination of security framework authentication server TKIP key management and Michael integrity checking aimed for enterprise use. The provides administrators with a variety of security implementations to establish authentication in which RADIUS is the de-facto. TKIP and Michael offer per-packet key mixing a message integrity check and a re-keying mechanism with efficiency. Consumer Mode - Pre-shared key PSK based protocol with the combination of Pre-Shared Key TKIP key management and Michael integrity checking aimed for home use. Simplicity of deployment is of primary concern. Mechanism Essential WPA tasks in Consumer Mode 1. associating with the access point AP 2. authentication and distribution of the PMK Pair-wise Master Key 3. creation and installation of the PTK Pair-wise Transient Key based on PMK 4. integrity check 5. a successful wireless session using TKIP based on PTK Vulnerability The PSK version of WPA suffers from an offline dictionary attack because of the broadcasting of information required to create and verify a session key. In WPA the
