Finding explanations about the various aspects of WPA2 suffers from inconsistent terminology and a general lack of clarity on what purpose some protocol/standard serves and how it relates to others.

I'm not looking for a total breakdown of every single part of WPA2, but I do have a few unanswered questions about it:

  1. What is the difference between "WPA2-Personal" and "WPA2-Enterprise"? Is "WPA2-PSK" synonymous with either one of these, is it an alternative to them, or is part of a different category?

  2. How are session keys established or "rotated"? How are they derived?

  3. How is the initiation of a WPA2 connection authenticated? Is a challenge-response scheme used?

  4. What cipher is used, what is the key size used for it, and what mode is it run in?


Most of this can be easily found on line. For the rest, your own phrasing is not clear as to what you mean.

  1. WPA-Personal

    Also referred to as WPA-PSK (pre-shared key) mode, this is designed for home and small office networks and doesn't require an authentication server. Each wireless network device encrypts the network traffic using a 256 bit key. This key may be entered either as a string of 64 hexadecimal digits, or as a passphrase of 8 to 63 printable ASCII characters. If ASCII characters are used, the 256 bit key is calculated by applying the PBKDF2 key derivation function to the passphrase, using the SSID as the salt and 4096 iterations of HMAC-SHA1. WPA-Personal mode is available with both WPA and WPA2.


    Also referred to as WPA-802.1X mode, and sometimes just WPA (as opposed to WPA-PSK), this is designed for enterprise networks and requires a RADIUS authentication server. This requires a more complicated setup, but provides additional security (e.g. protection against dictionary attacks on short passwords). Various kinds of the Extensible Authentication Protocol (EAP) are used for authentication. WPA-Enterprise mode is available with both WPA and WPA2.

  2. TKIP (Temporal Key Integrity Protocol)

    The RC4 stream cipher is used with a 128-bit per-packet key, meaning that it dynamically generates a new key for each packet. Used by WPA.

  3. There is a Question on crypto.SE going into detail on this.

  4. CCMP (CTR mode with CBC-MAC Protocol)

    The protocol used by WPA2, based on the Advanced Encryption Standard (AES) cipher along with strong message authenticity and integrity checking that is significantly stronger in protection for both privacy and integrity than the RC4-based TKIP used by WPA. Among informal names are "AES" and "AES-CCMP". According to the 802.11n specification, this encryption protocol must be used to achieve the fast 802.11n high bitrate schemes, though not all implementations enforce this. Otherwise, the data rate will not exceed 54 MBit/s.

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  • I edited the third question, but it seemed pretty straightforward: how do a wireless device and an access point authenticate each other when they initialize a connection? – Melab Apr 11 '16 at 14:26
  • @Melab, I edited my answer accordingly. – Tobi Nary Apr 11 '16 at 14:39

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