Enlarge / My DEF CON badge, complete with Wall of Sheep add-on from the DC801 crew, built by @kL34N and @SirGed. My puzzle quest is far from complete—it may require reprogramming and flipping a component. (credit: Sean Gallagher)

Nearly 30,000 people came to Las Vegas last week for the 26^th edition of DEF CON, the iconic security conference. And no small amount of the mental energy of that vast crowd was spent on one particular thing: the conference badge.

This year’s badges, designed by Tymkrs, were elevated works of printed circuit board art with a collection of LED-lit features, including red and green human figures and a color-shifting DEF CON logo. But it quickly becomes apparent that there was a lot more going on here than just blinking lights.

DEF CON alternates year to year between electronic, hackable badges and non-electronic ones; last year’s badges were a throwback design intended to celebrate the conference’s 25^th anniversary. But every year, the badges include some sort of clue to a cryptographic challenge—three years ago, the badge was an actual vinyl record that required attendees to find a turntable to hear the puzzle clue.