In case of WPA2 using the Radius server, every client gets its own username and password. But what is the case in the WPA2 using a PSK without the authenticating server. In this case also we have a 4 way handshake. But is the PTK derived by all clients different or the same?
The PTK is derived by all clients by using the following attributes: PMK (Pairwise Master Key), AP nonce (ANonce), STA nonce (SNonce), AP MAC address, and STA MAC address. That means that a different PTK will be derived for each 4 way handshake, although the PSK is the same.
But is the PTK derived by all clients different or the same?
Short answer: YES.
With WPA-PSK, you configure each WLAN node (access points, wireless routers, client adapters, bridges) not with an encryption key, but rather with a plain-English passphrase that contains up to 133 characters. Using a technology called TKIP (Temporal Key Integrity Protocol), that passphrase, along with the network SSID, is used to generate unique encryption keys for each wireless client.