Code breakers have discovered a technique for extracting a 104-bit Wired Equivalent Privacy (WEP) key in under a minute.

Cryptographic weaknesses with the first generation wireless encryption standard have been known for years, but the latest attack requires the capture of just a tenth of the number of packets required by previous approaches. The technique allows for 50 per cent probability of the recovery of a 104-bit WEP key in around a minute (on a 802.11g network running at full speed), and with the capture of 40,000 packets. Doubling the capture period extends the probability of capturing the key to 95 per cent.

Processing this data on a standard PC to reveal the key takes as little as three seconds, as explained in a paper by researchers Erik Tews and Ralf-Philipp Weinmann and Andrei Pyshkin of Darmstadt Technical University here. As before, the code breaking approach relies on exploiting cryptographic weaknesses in the RC4 stream cipher used by WEP that have been known about since 2001.

The latest attack illustrates the need to use the new WPA (Wi-Fi Protected Access) standard, which is far more resistant to attack, though infrequently used, even on wireless networks that employ any form of defences. ®

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