LAS VEGAS – For the last four years DefCon's badges have been designed with circuit boards that attendees have been encouraged to hack as part of a contest. This year, the badge hackers were competing to win a black über badge, which gives the recipient free entry to DefCon for life.

The contest badges were embedded with a microphone and digital signal processor connected to a full-color LED. The LED flashed and changed color in sync with the level and frequency of ambient sound.

About 30 contestants participated this year. Many of them spent days working on their creations using tools they brought with them or that were provided to them in the conference's hardware hacking area.

One contestant named Ben, who asked that his last name not be mentioned, created a frequency meter that he dubbed "the 15 output FFT." His badge uses a fast Fourier transform algorithm to compute the input frequency, which it then displays by lighting up one of the 15 LEDs.

One team of contestants, who called themselves "Optimized Tom Foolery," modified their badge with a Geiger counter-based random number generator with a wireless link. As the Geiger counter detected radiation, the badge used the sound ticks from it to generate random numbers, which were sent wirelessly via a Zigbee radio to a laptop. The number of random numbers generated varied depending on the amount of radiation detected by the Geiger counter.

One group of contestants, who achieved runner-up status, designed a badge-propelled blimp. The balloon was powered by three badges attached to motors. The dirigible used the built-in microphones on the badges to home in on the loudest source of sound and fly toward it.

But none of these ingenious hacks could beat the winner of the contest who used an array of LEDs soldered into a baseball cap to thwart facial recognition systems. His plan, theoretically, was to use the cap to sneak into the room of Joe "Kingpin" Grand – the designer of DefCon's badges – and steal the black über badges stored in his room.

This year, the DefCon badge wasn't the only electronic badge at the conference. Ninja Networks, which throws a popular party each year at the conference, produced an electronic badge of its own to gain access to its party.

Over 500 badges were made by hand. The badges featured ten segmented LED displays, four buttons and several microchips on the back. Once powered on, the LED's blinked random, scrambled letters that froze to form the words "NINJA PARTY" after 100 seconds. The badge was also programmed with a game of Simon-Says. Owners could alter random segments of the badge's memory through a keypad on the badge.

The badges were created by Amanda Wozniak, who designed the circuitry, and Brandon Creighton, who wrote the badge firmware.

Most of the work on the badges was completed in Boston before the conference, but workers scrambled to finish some of the final soldering in their DefCon hotel room in the days before the party.

Photos: Dave Bullock

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