Easiest Way to Verify Location?

Question

I'm interested in creating a product (e.g. something that works with Meetup.com) that would require us to verify they went to the meetup location. This should be as seamless as possible for the user, preferably without them downloading a new app.How could we: A) allow the meetup organizer to ping phones to verify the people that went to the meetupB) use Google Maps to allow users to give us a one-time ping of their locationEdit: We'd essentially reward the organizers for getting people to show up. We want it to be as difficult as possible for them to game.Much appreciated

Nextgrid · Accepted Answer

What is the threat model? Do the organisers have an incentive to cheat? Do invitees have one?
If the organisers can be trusted then the solution is to have a device displaying a QR code that rotates regularly (30 seconds?) at the location and have attendees scan it.
If the invitees can be trusted then the process can be reversed. Each invitee displays an unique QR code during check-in the organiser should scan.
If neither can be trusted then you’d need a neutral third-party to act as a witness by scanning both the organiser’s code and the invitees’. This proves that the witness was at the event (and it was indeed open to the public) and that invitees did show up.
Out of curiosity, how do you prevent a malicious party from creating dozens of fake accounts and using them to check in at their fake event?

phillipseamore · Answer

Keep it simple. Have a sign with a QR code to check in.