http://code.google.com/p/pyrit/
WPA/WPA2-PSK is a subset of WPA/WPA2 that skips the complex task of key distribution and client authentication by assigning every participating party the same pre shared key. This master key is derived from a password which the administrating user has to pre-configure e.g. on his laptop and the Access Point. When the laptop creates a connection to the Access Point, a new session key is derived from the master key to encrypt and authenticate following traffic. This "shortcut" eases deployment of WPA/WPA2-protected networks for home- and small-office-use at the cost of making the protocol vulnerable to brute-force-attacks against it’s key negotiation phase; it allows to ultimately reveal the password that protects the network. This vulnerability has to be considered exceptionally disastrous as the protocol allows much of the key derivation to be pre-computed, making simple brute-force-attacks even more alluring to the attacker.
Pyrit allows to create massive databases, pre-computing part of the WPA/WPA2-PSK authentication phase in a space-time-tradeoff. Exploiting the computational power of Many-Core- and other platforms through ATI-Stream, Nvidia CUDA, OpenCL and VIA Padlock, it is currently by far the most powerful attack against one of the world’s most used security-protocols. For more background see this article on the project’s blog.
The author does not encourage or support using Pyrit for the infringement of peoples’ communication-privacy. The exploration and realization of the technology discussed here motivate as a purpose of their own; this is documented by the open development, strictly sourcecode-based distribution and ‘copyleft’-licensing.
Pyrit is free software – free as in freedom. Everyone can inspect, copy or modify it and share derived work under the GNU General Public License v3+.