Private PSK (PPSK) Overview

• Private Pre Shared Key (PPSK) is a function that allows multiple WiFi keys to be used for a single SSID.
• It can be compared to a door that can be unlocked by people with different keys to gain access to a building.
• This is in contrast to a door where everyone has the same key to unlock it and gain access to a building.
• The advantage of using different keys is the ease of management.
• If you have a small office setup where an employee perhaps leave the company on a bad foot and you want to make sure they do not get access to the WiFi network.
• Without the support of Pre Shared Key you need to:
  • Change the shared key on the access point(s).
  • Inform all employees that the WiFi key has changed and hopefully they will be smart enough to update any devices that are configured to connect to the office WiFi network.
  • Another place where you need to update the WiFi key is any peripherals that are connected to the network, including printers, scanners and cameras.
• With pre-shared key support, you simply revoke the PPSK of employees.

• The PPSK function has been around for a long time.
• Aerohive (now Extreme Networks) was probably the first vendor to come up with this feature more than 8 years ago.
• Most enterprise vendors have caught up and added the feature, but some have ignored the request for this feature for years. (Here you can see a post where the Ubiquity community asked for this feature 7 years ago)
• Ubiquity finally implemented the feature in Unifi in 2023.
• This was probably because TP-Link's Omada already included the feature and some of the Ubiquity customers who wanted the feature then opted for Omada.
• However, the Ubiquity implementation does not include a RADIUS option, whereas the Omada implementation does.
• Some people think Omada is a copy of Unifi. With PPSK, we can definitely say that Omada took the initiative before Unifi.
• Each vendor has its own unique implementation and sometimes its own terminology.
  • Cisco calls it Identity PSK.
  • Aruba calls it Multiple Pre-Shared Key (MPSK).
  • Ruckus calls it Dynamic PSK.
• Some of the names and technologies are trademarked and protected.
• Under the hood, however, most providers that have recently added the PPSK function use the hostapd programme.
• hostapd is an open source authenticator for WiFi APs.
• This feature offers two main functions.
  • The ability for each device that connects to a single SSID to have a unique WPA2 shared key.
  • The ability for each device to be assigned to a predefined VLAN after authentication.

Your next question might be “OK, so why would I want to use this feature?” or even “Where do you use this feature?”

• The Private PSK allows you to use secure, device-bound credentials.
• This allows clients to securely authenticate and join the network using a specific device and PSK combination.
• This enhances security and deployment flexibility for headless IoT devices.
• Optional dynamic VLAN assignment further enhances the security and manageability.
• RADIUSdesk is used to centrally manage device and PSK matching.
• A PSK on the device owner's profile is the most generic solution.
• A more granular option will be a PSK on the device owner.
• Finally there is an option for a PSK on the device itself.
• Other features included with RADIUSdesk are available also to use:
  • Future date activation.
  • Expiry date.
  • Time slots when the network can be used by the device.
• One SSID can support all these features.
• Using one SSID improves bandwidth utilization and provides a simplified user experience.
• The easy to use on-boarding Captive Portal minimize support calls.

• We will split this into two categories. One for small deployments and another for large deployments.

• In a small deployment you need a minimum of one Access Point.
• Private PSK is also supported in the mesh networks managed by MESHdesk.
• You don't need any VLAN aware equipment, the VLAN assignment will be internal.
• You will typically have:
  • A Single SSID that is configured for Private PSK security.
  • The On-boarding Captive Portal.
  • A LAN bridge
  • Zero or more NAT+DHCP networks
  • Zero or more OpenVPN bridges.
• Includes small offices or home deployments

• With large deployments you can potentially have thousands of Access Points all centrally managed using MESHdesk and APdesk.
• These deployments will include working together with other components to provide an integrated solution.
• You will typically have
  • A common SSID that is configured for Private PSK security on all the Access Points.
  • External / Central on-boarding Captive Portal.
  • Multiple VLAN enabled switches.
  • A firewall that hosts multiple networks, each of which is linked to a different VLAN.
• Includes Multiple Dwelling Units (MDU), Schools, hotels and conference facilities and WiFi networks with IOT devices.

• WPA2 Enterprise are definitely more secure but there are two issues which usually turn people off from implementing it.
• Certificate management. The Certificate Authority (CA)'s certificate needs to be installed on the client connecting.
• Not all WiFi devices support it.
  • Many IOT devices do not support WPA2-Enterprise
  • Many printers and WiFi cameras do not support WPA2-Enterprise.
• RADIUSdesk along with MESHdesk and APdesk however also offer WPA2 Enterprise support should you wish to rather implement it instead of Private PSK.