Generating the PMK using the PBKDF2 function is slow and costly.

MIC = HMAC_MD5(MIC Key, 16, 802.1x data)Ī MIC value is calculated, using the MIC Key from the PTK and the EAPoL message.

The PTK is a keyed-HMAC function using the PMK on the two MAC addresses and the two nonces from the first two packets of the 4-Way Handshake.

PTK = PRF-512(PMK, 'Pairwise key expansion', Min(AP_Mac, Client_Mac) || Max(AP_Mac, Client_Mac) || Min(ANonce, SNonce) || Max(ANonce, SNonce)).

Īnd the other PTK hash is generated using this less processor intensive function, pseudo code: The lengths of the passphrase and the SSID have little impact on the speed of this operation. Passphrase, SSID, and the SSIDlength is hashed 4096 times to generate a value of 256 bits. This means that the concatenated string of the Where the PBKDF2 method is from PKCS #5 v2.0: Password-based Cryptography Standard.

PMK = PBKDF2(passphrase, ssid, ssidLength, 4096, 256).

The PMK is generated using the following relatively processor intensive function, pseudo code:

AP sends an acknowledgment to the client signed with the Pairwise Transient Key and includes information for further communicationįor an excellent explanation, see the Airolib-ng manual.

If it's the same, the AP can then assume the client used the same Pairwise Master Key (Password+ESSID) to generate the Pairwise Transient Key, subsequently used to sign the message.

By signing the SNonce message with the new Pairwise Transient Key, the AP can match the Integrity Code of the SNonce message sent from the client.

Use the Pairwise Master Key, ANounce, SNounce, and AP and client MAC address to compute a Pairwise Transient Key AP receives the signed SNonce, and compute the Pairwise Master Key from its Password and ESSID.Client will sign the SNonce number using the Pairwise Transient Key and send it unencrypted to the AP.Client create a random SNonce number, take the Pairwise Master Key, ANonce, SNonce, and AP and client MAC address to compute a Pairwise Transient Key.AP will responds with a random ANonce number.Client will take the Password and ESSID of the network to compute a Pairwise Master Key and send a request to the AP asking to connect.When a client want to connect to a access point, the following simplified stages will take place:

While the 802.11i standard, of which WPA is implemented on, is still intact the authentication is prone to a offline brute-force attack. a common password between the Access Point and Client Station, for protection. Most wireless networks operating today use WPA and a Pre-Shared Key (PSK) between parties, i.e.

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