4 ms·

Phones do this to authenticate faster to known access points. Instead of waiting for an SSID beacon, they just broadcast their known networks and if one of the

Phones do this to authenticate faster to known access points. Instead of waiting for an SSID beacon, they just broadcast their known networks and if one of them is in range, the AP will reply. It's all driven by user demand to connect to their WiFi network faster. Also, AFIAK, this is required behaviour to join networks that don't broadcast their SSID (e.g. "hidden" networks). I see two solutions to this problem, but neither are really tenable from a user perspective: 1) run the GPS all the time and geotag known APs[1] 2) leave the WiFi radio on all the time and passively listen for SSID broadcasts[2] [1] doesn't work indoors, or if the location of an AP is changed (e.g. 4G hotspot). Will also have significant impact on battery runtime, and likely to be abused by ad companies [2] will have significant impact on battery runtime

schoen 11y ago
It's hard to solve this part of the problem using current wifi protocols. I think this is closely related to other problems that people have studied and I'm sure protocol improvements could be made using public-key crypto or HMAC. As an off-the-cuff example, when you join an encrypted network, it could tell you (over the encrypted channel) a shared secret to use when reconnecting. Then you could broadcast HMAC(secret, current time) or (nonce, HMAC(secret time, nonce)) and if the wifi network recognizes one of those broadcasts as directed to it, it could reply. An eavesdropper who doesn't know the secret wouldn't be able to determine which base station the mobile device was trying to contact.