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Does having a complex preshared key improve the security of WPA2-PSK, or is having even a simple PSK enough to secure the wireless network?

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    What is your threat model? – Xander Jan 2 at 2:26
  • Attacker can capture the key exchange on air, then brute-force to obtain passphrase. If passphrase is hard enough then it will take attacker forever to break. – daygoor Jan 2 at 7:57
  • With PSK it's especially important to use a strong password as there's no "three wrong passwords and account locked" – paj28 Jan 2 at 20:53
  • For what it's worth, what inspired this question was a local restaurant employing a phone number for the wireless network provided to guests. – Davidw Feb 28 at 4:07
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A strong passphrase is better than a weak one.

On a WPA2-protected network with a simple passphrase, a naive attacker would be deterred - but a sophisticated attacker would not (because they could simply capture the handshake and crack the passphrase).

On a WPA2-protected network with a complex passphrase, even a sophisticated attacker would be deterred (for that particular attack path, anyway) - because they wouldn't be able to crack the passphrase.

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As @Xander says, it depends on your attacker, but WPA2-PSK protected with a weak password can be more easily cracked than a strong one.

The reason I make this statement is that tools for brute force cracking WiFi can take a wordlist as input. To break into WiFi, a hacker can take the following steps:

  1. Do some info gathering on your target. Find their access point, learn their interests.
  2. Use airodump-ng to capture packets from the access point while simultaneously sending de-auth packets from another network adapter, causing legitimate traffic to drop and reconnect. With patience and luck, airodump-ng will capture the new key exchange during the reconnection process, giving the info needed to test their key guesses.
  3. Compile a wordlist of password guesses. They may have chosen a password related to their family, hobby, etc. You can also obtain wordlists of common passwords online. This is where a weak password will fall.
  4. Use hashcat to test your wordlist of guesses on the captured handshake packets.
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In addition to the response from @Royce Williams and John Deters

I would like to add few more details on how WPA2-PSK in action to improve the security posture of the wireless network.

WPA2 is improvement of WPA I and IEEE numbering is 802.11i and called as Robust Security Network (RSN).

Here is very specific flow diagrams of WPA2-PSK (4-way handshake) for your understanding and encourage you to read the rest of slides.

http://image.slidesharecdn.com/crackingwpa2-pskinthecloud-110505163725-phpapp01/95/cracking-wpa2-psk-in-the-cloud-3-728.jpg?cb=1304614211

enter image description here

Generate your passphrase by cryptographic random functions with combination of upper, lower, numbers & special characters with length more than 12 characters and supports up to 63 ASCII printable characters (this is according to the 802.11i specification).

Apart from PSK length also consider to enforce wireless security by design e.g.

  1. Limiting the SSID broadcasting to specific regions/floors/area

  2. Exchange of PSK key by HEX instead of plain text

  3. Implement 802.1x wired authentication for wireless access point to protect from adding ad-hoc/rouge access points into the wireless network

  4. Improve monitoring and alerting of wireless network

These generally should able to protect your wireless network security whilst improving the PSK keys.

You should also be aware that WPA2 4-way handshake is "security by obscurity" and KRACK has demonstrated the ways to attack WPA2 4-way handshake. WPA3 with improved security by adding Forward-Secrecy (Concept of SSL/TLS) and also PSK key exchange function. Wifi Alliance announced in Jan-2018 - kindly check with your vendor for WPA3 availability

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    WPA2 is not an improvement of WPA. WPA was a WFA certification provided to quickly resolve WEP security issues based on an early draft of 802.11i. WPA2 is the WFA certification of the ratified 802.11i IEEE ammendment. Also, KRACK exploited a flaw in some client implementations of the WPA2 handshake, but does not in any way compromise the original PSK. – YLearn Jan 2 at 20:20
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There are a number of methods for attacking a wireless network, most having to do with capturing the WPA2 handshake and brute forcing based on the information captured. A more efficient method attacking the PMKID with a brute force attack (in networks with features that enable the RSN PMKID being included in EAPOL frames) has been found/published in the last six months.

Either of these methods require brute forcing the data captured to see if the tested value can produce the "correct key." If your PSK is a simple dictionary word, then this will likely be a quick process. If your PSK is a long and complex, it will typically be much harder to compute.

Does having a complex preshared key improve the security of WPA2-PSK, or is having even a simple PSK enough to secure the wireless network?

Depends on the needs of your wireless network. If you are likely to be targeted by skilled and knowledgeable people with the right hardware, then a simple PSK will not be sufficient.

If you are like one of my friends living in Montana (with a house 3/4 of a mile off the main road and no neighbors for miles in any direction), then a simple PSK will likely be more than sufficient.

Odds are you are somewhere in the middle, so your PSK should be at least somewhere in the middle. For best security though, always error on the side of making it more difficult for an attacker, so choose a longer and more complex password.

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