Guest Lecture: Plaintext Recovery Attacks Against WPA/TKIP

Speaker: Prof. Kenny Paterson, Royal Holloway, University of London
UCL Contact: Steve Marchant (Visitors from outside UCL please email in advance).
Date/Time: 22 Jan 14, 14:00 - 15:00
Venue: Cruciform B404

Abstract

We conduct an analysis of the RC4 algorithm as it is used in the IEEE WPA/TKIP wireless standard. In that standard, RC4 keys are computed on a per-frame basis, with specific key bytes being set to known values that depend on 2 bytes of the WPA frame counter (called the TSC). We observe large, TSC-dependent biases in the RC4 keystream when the algorithm is keyed according to the WPA specification. These biases permit us to mount a statistical, plaintext-recovering attack in the situation where the same plaintext is encrypted in many different frames (the so-called ``broadcast attack'' set