ream. In this Stubblefield, Ioannidis, and Rubin implemented the al- fashion one can accumulate cipher streams for packet gorithm and showed that keys could be extracted after injection or other attacks. interception of on the order of 1,000,000 packets. Wireless local area networks CHAPTER 5.1 Finally, we should note that there is no provision data rates, SO there are no repeated cipher streams to whatsoever in the standard to allow a client to authen- intercept. A sophisticated integrity checking mechanism ticate the access point to which it is associating, so that an is also included to guard against an attacker injecting attacker with a shared key can set up a spoof access point slight variations of valid transmitted packets. and intercept traffic intended for a legitimate network. WPA addresses all the currently known attacks on All the above attacks depend on another weakness in WEP, though total security also depends on proper se- the standard: no provision was made for how the shared lection and implementation of algorithms within the secret keys ought to be exchanged. In practice, this meant 802.1x authentication process. It is certainly secure that in most systems the secret keys are manually entered enough for home networks and for most enterprise/in- by the user. Needless to say, users are not eager to change dustrial implementations. At the time of this writing their keys every week, to say nothing of every day, and (mid-2004), the 802. lli task group has approved an manual reentry of shared keys more than once an hour is enhanced standard based on the Advanced Encryption impractical. Further, manual key exchange over a large Standard rather than the WEP RC4 algorithm, which will community of users is an administrative nightmare. As provide an adequate level of security for most uses. a consequence, it is all too likely that WEP shared secret Enterprises that have serious concerns about sensitive keys will remain fixed for weeks or months at a time, data can also implement end to end security through