  This paper presents new attacks against TKIP within IEEE 802.11 based
networks. Using the known Beck-Tews attack, we define schemas to con- tinuously
generate new keystreams, which allow more and longer arbitrary packets to be
injected into the network. We further describe an attack against the Michael
message integrity code, that allows an attacker to concatenate a known with an
unknown valid TKIP packet such that the unknown MIC at the end is still valid
for the new entire packet. Based on this, a schema to decrypt all traffic that
flows towards the client is described.

Cryptography and Security