请参考这篇文章：
1. start reaver attack using any random bssid and after 1 or two pin attempts, prezz Ctrl+Z to stop the process.
2. Now goto /usr/local/etc/reaver folder and there you will see the .wpc file with that random bssid you just attacked on.
3. Provided that you have noted the target bssid for which you had lost the session file, change the name of this wpc file to that bssid, e-g from 8C0CA32B19D7.wpc to 001122334455.wpc(assuming that my target bssid id I was working on before was 00:11:22:33:44:55)
4. Now open this wpc file in any text edtitor and you will see the keys written as i told above, but
5. In first line is the pin which reaver was cracking, let say you remembered it or you knew the average percentage reaver was completed. Let say 49%.
6. Now from that we can assume that there are 10,000 combinations first, and it was done 49% so ping might be somewhere around 4900.
7. Just change that pin in first line to 4900 or any closest according to the analysis.
8. 2nd and 3rd lines are saying 0 and 0 and rest are combinations.
9. Save the file.
10. start reaver with that exact target bssid which you were working on before.
11. Voila, say thanks to me in your heart because i can see that smile of winning on your face :P
http://www.backtrack-linux.org/forums/showthread.php?t=62523