Take a minute to visit https://map.what3words.com/ or my post Wrigley Field: 1060 W Addison St, Chicago, IL or digits.bucked.talent? (3-Word Addresses), or this post won’t be as useful as it could be.
In a nutshell, https://map.what3words.com/ has created a 3 by 3 meter grid on the Earth’s surface and assigned each block a three-word name. For the convenience of people accustomed to more conventional addresses, where available, you can submit an address and get the three-word name for that block back.
Excellent potential for a project name “Mis-Direction,” that needs an innocent name as a smartphone app.
You send someone a three-word block name and when displayed on their smartphone, it maps to the “canonical” location. Anyone using your phone will get that result.
However, if when the location is displayed, without a prompt or signal, if you enter a 5-digit code, the actual location intended by the sender is revealed.
Would require a mapping table between 3-word name as sent and 3-word name as intended, and the locations have to be plausible to any third party who might be tracking the communication or using your phone.
I would suggest allowing 5 tries to get the correct number because locations for demonstrations and other activities need to be operationally secure for only a matter of hours.
After that, anyone can follow the trail of emergency vehicles to a location that was a closely held secret only hours before.
It isn’t clear if the uptake on What3Words will be broad enough to have an impact at large political gatherings in the United States this year but the same re-mapping principle with password applies to more conventional mapping techniques as well.