hello you need cpyrit which does not get install with pyrit from repo (did not work for me) download pyrit 4.0 build&install http://code.google.com/p/pyrit/
:~# pyrit list_cores
Pyrit 0.4.0 (C) 2008-2011 Lukas Lueg http://pyrit.googlecode.com
This code is distributed under the GNU General Public License v3+
The following cores seem available...
#1: 'CUDA-Device #1 'GeForce GTX 560''
#2: 'CPU-Core (SSE2)'