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What’s the difference between the process of attacking WPA and the process of attacking WPA2?

I know that WPA2 is much more secure than WPA. However, it seems the case that both of them are attacked using the same mechanism — basically, capturing the handshake and then doing brute-force. Are both protocols equally vulnerable to brute-force?

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WPA was just a quick update to WEP protocol to solve some security problems until the final version of 802.11i standard was delivered.

The message integrity check, per-packet key hashing, broadcast key rotation, sequence counter and key mixing function were updated from WEP in order to patch some of the current vulnerabilities. This is why in some cases, WPA is considered to be a draft of 802.11i standard.

The main difference between WPA and WPA2 is the encryption protocol used:

  • TKIP used by WPA, still uses RC4 cipher as WEP, so apart from the patched vulnerabilities it has some new ones like MIC key recovery and an extended version of chop-chop WEP attack.

  • WPA2 was the final implementation of 802.11i and it introduces a new encryption protocol CCMP. This new protocol uses a stronger cipher AES-256, which represents a huge improvement from RC4.

Aside from this main difference, both WPA and WPA2 uses the same key exchange mechanism. The 4-way handshake is used to exchange encryption keys, so therefore this is why you can attack WPA/WPA2 in the same way, by capturing its handshake and bruteforcing PMK/PTK:

sequence diagram

The attacker tries various passphrases, computes PMK and PTK using those passphrases, and then verifies the MAC in order to check if the passphrase was correct.

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  • 4
    For a moment I had to stop and think what "chiper" was :)
    – Martin Argerami
    Aug 22, 2016 at 12:15
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    @MartinArgerami It's the woodchipper that you're supposed to feed the computer of a developer who thinks they know enough to roll their own crypto.
    – Nzall
    Aug 22, 2016 at 13:32
  • So TKIP is not an encryption algorithm on its own? Its just some iteration of RC4?
    – Minaj
    Aug 22, 2016 at 15:41
  • Do both WPA and WPA2 use the same size of encryption key? I am trying to asses if the required brute-force effort is the same in both cases.
    – Minaj
    Aug 22, 2016 at 15:53
  • @Minaj TKIP is an encryption protocol that IEEE 802.11i task group designed in order to correct the WEP vulnerabilities without requiring to upgrade the hardware. This is why TKIP still uses RC4 cipher, but also some new features where implemented in order to correct the WEP vulnerabilities. This was just a "fast" patch until the new version could be released (WPA2 with CCMP).
    – z4k4
    Aug 22, 2016 at 19:42
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The authentication mechanism is same, but the difference between WPA and WPA2 is the encryption protocol used.

WPA uses the TKIP protocol while WPA2 introduces support for the CCMP protocol.

And it's worth mentioning that timing attacks against TKIP have been successful. check this.

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