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In a microcontroller powered by a solar cell we need to have the current time. When the sun decrease the micro-controller switch off and all the volatile data vanish. When the sun increase the micro-controller reboot and we need to set the time on reboot.

I had an idea but I do not know enough wifi to be sure it's feasible : Getting the current time from the surrounding wifi signals.

In this post How much information can be gathered about a network without connecting? you can get :

  • ESSIDS BSSIDS
  • Crypto strength and authentication scheme (Pre shared Key vs EAP/Radius)
  • Signal strength
  • ....

But I can't see if the AP current time is obtainable ?

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    I'm voting to close this question as off-topic because it is unrelated to information security how to retrieve the current time from WiFi. Related to security would for example be a question on how reliably these information are in case one needs to use the time for security relevant synchronization with other devices. – Steffen Ullrich Jan 29 '17 at 14:30
  • afaik, you would need to connect to the wifi or use a cheap ($1usd) RTC module with the MCU. EDIT: one trick i thought of: you could broadcast the time as a hotspot SSID, ex: "dt_0645" for 6:45AM. that way, you only need scan and not connect. how you customize that ssid i'll leave up to you, but it could be greasemonkey on router admin page or some cheap AP like a single-purpose ESP8266 . – dandavis Jan 29 '17 at 22:38

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