from arstechnica.com

Your home or office WiFi network may be even less secure than you think. Researchers have now shown that they can break 104-bit WEP, a common 802.11b/g/n security mechanism, in as little as one or two minutes. A team at the Technische Universität Darmstadt said that they can grab the key with a 95 percent probability of success in as little as two minutes using a 1.7GHz Pentium-M machine to do the calculations.

Here’s how the attack works: in order to find the key, a would-be attacker has to have enough traffic to analyze. Therefore, the researchers forced the protected network to start generating packets. Once they have 40,000 packets to analyze, they have a 50 percent success rate in grabbing the key; an additional 20,000 packets nudges the success rate up to 80 percent. Reaching the 95 percent threshold requires 85,000 data packets. As they were able to generate 764 packets per second, they were able to hit the 85,000 mark in 1:51. At this time, the researchers’ tool, aircrack-ptw (source code)—which they say is similar to aircrack-ng—does not work on 256-bit WPA.