2 ms·

> It's even more unfortunate that the committees designing these protocols don't think this way. So. How would you design a system to permit associated or unas

> It's even more unfortunate that the committees designing these protocols don't think this way. So. How would you design a system to permit associated or unassociated stations to passively determine whether or not they were in range of a given AP? Remember that unassociated stations may never have ever interacted with the AP in question before this moment.

mindslight 11y ago
That's the easy part. If previous contact hasn't taken place, persistence is irrelevant. Simply envision the current system with a periodically changing BSSID as your proof of existence. If the AP and client possess a shared secret (as in WPA2), then there's no reason for a third party to be able to deduce any identifying information.
- simoncion 11y ago
  > That's the easy part. If previous contact hasn't taken place, persistence is irrelevant. A periodically-changing ID would do. Okay. How would you design a system to permit associated or unassociated stations to passively determine whether or not they were in range of a given AP? Remember that human-friendly names for a given AP are almost certain to collide.
  - mindslight 11y ago
    First, for purposes of this comment I only need to address the situation where WPA2 is currently used (the majority of private APs). Second, I'm one person taking a few minutes to write a HN comment, not a design committee. Simple protocol: The AP and client have shared secret K (similar to the present WPA2 key). We define the identity of a network as this secret key. The AP can change "BSSID" every hour, while broadcasting [BSSID, Hash(BSSID, K)]. An interested client runs through their database of known private networks, checking if the broadcaster is any they know. This obviously has a number of shortcomings (eg our attacker is also known to groom people into uploading K to their silos), but it should illustrate the concept.
    - simoncion 11y ago
      > An interested client runs through their database of known private networks, checking if the broadcaster is any they know. That solves the problem for clients that have connected to that AP before. [0] How do you propose to solve the problem for clients that have never interacted with that AP before? [0] It probably actually doesn't, but I won't distract you with why at the moment. :)
      - mindslight 11y ago
        As I said originally, just change the BSSID periodically. The network name is the network identity, and people deal with collisions just fine. Also, this is back to the case of non-WPA2 (otherwise the user would have to enter the secret K anyway, merely changing the process slightly).
        simoncion 11y ago
        > Also, this is back to the case of non-WPA2... Okay, I'm a little confused, please bear with me. Are you designing two half systems, one of which periodically changes BSSID but provides no other anonymity protection, and the other which hashes the BSSID with the WPA2 PSK? Or are you designing one system with a rotating BSSID that transmits -in cleartext- the BSSID and the hashed BSSID?
        mindslight 11y ago
        I'm pointing out existence certificates of each independent property. View them as two systems, or assume they can be merged into one system. It's obviously impossible to have a publicly-available network that hides its existence to the public (while a private network can obviously hide its existence to the public completely), so each problem will obviously have different ideal solutions.
        simoncion 11y ago
        > View them as two systems, or assume they can be merged into one system. It's the merging and the details of the same that's the complicated bit, and the only thing worth talking about in this sub-thread. You made the assertion that the "the committees designing [wireless communications] protocols don't think [that things screamed on the street corner are public data]". [0] This is simply not true. The folks who designed 802.11 had to make several key-management-complexity/computational-power/ease-of-use tradeoffs. > ...while a private network can obviously hide its existence to the public completely... Not if it's a relatively-high-performance radio network operating in a relatively tiny slice of spectrum, [1] it can't. [0] https://news.ycombinator.com/item?id=10950276 https://news.ycombinator.com/item?id=10950276 [1] As 802.11b/g/n does

mindslight 11y ago

That's the easy part. If previous contact hasn't taken place, persistence is irrelevant. Simply envision the current system with a periodically changing BSSID as your proof of existence. If the AP and client possess a shared secret (as in WPA2), then there's no reason for a third party to be able to deduce any identifying information.

simoncion 11y ago
> That's the easy part. If previous contact hasn't taken place, persistence is irrelevant. A periodically-changing ID would do. Okay. How would you design a system to permit associated or unassociated stations to passively determine whether or not they were in range of a given AP? Remember that human-friendly names for a given AP are almost certain to collide.
- mindslight 11y ago
  First, for purposes of this comment I only need to address the situation where WPA2 is currently used (the majority of private APs). Second, I'm one person taking a few minutes to write a HN comment, not a design committee. Simple protocol: The AP and client have shared secret K (similar to the present WPA2 key). We define the identity of a network as this secret key. The AP can change "BSSID" every hour, while broadcasting [BSSID, Hash(BSSID, K)]. An interested client runs through their database of known private networks, checking if the broadcaster is any they know. This obviously has a number of shortcomings (eg our attacker is also known to groom people into uploading K to their silos), but it should illustrate the concept.
  - simoncion 11y ago
    > An interested client runs through their database of known private networks, checking if the broadcaster is any they know. That solves the problem for clients that have connected to that AP before. [0] How do you propose to solve the problem for clients that have never interacted with that AP before? [0] It probably actually doesn't, but I won't distract you with why at the moment. :)
    - mindslight 11y ago
      As I said originally, just change the BSSID periodically. The network name is the network identity, and people deal with collisions just fine. Also, this is back to the case of non-WPA2 (otherwise the user would have to enter the secret K anyway, merely changing the process slightly).
      - simoncion 11y ago
        > Also, this is back to the case of non-WPA2... Okay, I'm a little confused, please bear with me. Are you designing two half systems, one of which periodically changes BSSID but provides no other anonymity protection, and the other which hashes the BSSID with the WPA2 PSK? Or are you designing one system with a rotating BSSID that transmits -in cleartext- the BSSID and the hashed BSSID?
        mindslight 11y ago
        I'm pointing out existence certificates of each independent property. View them as two systems, or assume they can be merged into one system. It's obviously impossible to have a publicly-available network that hides its existence to the public (while a private network can obviously hide its existence to the public completely), so each problem will obviously have different ideal solutions.
        simoncion 11y ago
        > View them as two systems, or assume they can be merged into one system. It's the merging and the details of the same that's the complicated bit, and the only thing worth talking about in this sub-thread. You made the assertion that the "the committees designing [wireless communications] protocols don't think [that things screamed on the street corner are public data]". [0] This is simply not true. The folks who designed 802.11 had to make several key-management-complexity/computational-power/ease-of-use tradeoffs. > ...while a private network can obviously hide its existence to the public completely... Not if it's a relatively-high-performance radio network operating in a relatively tiny slice of spectrum, [1] it can't. [0] https://news.ycombinator.com/item?id=10950276 https://news.ycombinator.com/item?id=10950276 [1] As 802.11b/g/n does