Time for action – speeding up the cracking process

We can proceed with the following steps:

  1. We can precalculate the PMK for a given SSID and wordlist using the genpmk tool with the following command:
    genpmk –f <chosen wordlist>–d PMK-Wireless-Lab –s "Wireless Lab

    This creates the PMK-Wireless-Lab file containing the pregenerated PMK:

    Time for action – speeding up the cracking process
  2. We now create a WPA-PSK network with the passphrase abcdefgh (present in the dictionary we used) and capture a WPA-handshake for that network. We now use Cowpatty to crack the WPA passphrase, as shown in the following screenshot:
    Time for action – speeding up the cracking process

    It takes approximately 7.18 seconds for Cowpatty to crack the key, using the precalculated PMKs.

  3. We now use aircrack-ng with the same dictionary file, and the cracking process takes over 22 minutes. This shows how much we are gaining because of the precalculation.
  4. In order to use these PMKs with aircrack-ng, we need to use a tool called airolib-ng. We will give it the options airolib-ng, PMK-Aircrack --import,and cowpatty PMK-Wireless-Lab, where PMK-Aircrack is the aircrack-ng compatible database to be created and PMK-Wireless-Lab is the genpmk compliant PMK database that we created previously.
  5. We now feed this database to aircrack-ng and the cracking process speeds up remarkably. We use the following command:
    aircrack-ng –r PMK-Aircrack WPACrackingDemo2-01.cap
  6. There are additional tools available on BackTrack such as Pyrit that can leverage multi CPU systems to speed up cracking. We give the pcap filename with the -r option and the genpmk compliant PMK file with the -i option. Even on the same system used with the previous tools, Pyrit takes around 3 seconds to crack the key, using the same PMK file created using genpmk.

What just happened?

We looked at various different tools and techniques to speed up WPA/WPA2-PSK cracking. The whole idea is to pre-calculate the PMK for a given SSID and a list of passphrases in our dictionary.

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