4 ms·

> 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 sy

> 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
        Merging them really only means merging the concepts for a common model of administration. Public and private are two completely different modes, and don't exist simultaneously. A high-bandwith radio transmitter obviously gives its presence up, but that doesn't mean it needs to identify itself. Of course the FCC likes transmitters to do this, but that too is an anti-feature with respect to public-use spectrum. There were obviously tradeoffs involved for 802.11, which is how we got WEP. I'd just be surprised if having a (semi-)fixed MAC address was ever questioned, given that it's the basis for 802.3 and leaking some associated identity is basically a forgone conclusion in today's world of license plates, etc. But with the obvious effects of mechanized tracking and aggregation, it really shouldn't be. So I stand by my assertion that the designers would have benefited from a perspective where being pushed to do the equivalent of continually shouting/showing one's identity is a very bad thing.

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
        Merging them really only means merging the concepts for a common model of administration. Public and private are two completely different modes, and don't exist simultaneously. A high-bandwith radio transmitter obviously gives its presence up, but that doesn't mean it needs to identify itself. Of course the FCC likes transmitters to do this, but that too is an anti-feature with respect to public-use spectrum. There were obviously tradeoffs involved for 802.11, which is how we got WEP. I'd just be surprised if having a (semi-)fixed MAC address was ever questioned, given that it's the basis for 802.3 and leaking some associated identity is basically a forgone conclusion in today's world of license plates, etc. But with the obvious effects of mechanized tracking and aggregation, it really shouldn't be. So I stand by my assertion that the designers would have benefited from a perspective where being pushed to do the equivalent of continually shouting/showing one's identity is a very bad thing.