Cyphercon 4.0 came to life in Milwaukee, Wisconsin on Thursday and the conference badge is a brilliant and engaging design. At first glance it looks like a fairly mundane rectangular badge. But a closer look reveals simplistic elegance wrapping around some clever mechanical design and the awesome interactive mechanism of being able to read paper tape.

That’s right, this badge can read the series of holes punched in the long paper strips you normally associate with old iron of 50 years ago.

This is a design by the @tymkrs, the team who designed last year’s DEF CON 26 badge and the previous Cyphercon badges. This one is made up of three different panels placed vertically. The top is the Semaphore panel (named so because it’s printed on the silk screen) which includes an array of 25 LEDs arranged in groups of five. Just above that you’ll see the horseshoe-shaped holes. These are consumables, parts of the substrate clipped off with angle cutters when you visit the paper tape punching machine — it limits the number of times you can get these tapes made to hack your badge. The next panel down is the one with “Cyphercon 4.0” on the front and the coin cell battery on the rear. The final panel is the tape reader and the logic circuitry.

Paper tape feeding through the badge Logic circuit includes IR sensors for reading the tape

Along the right edge of the tape reader you can see the array of IR emitters and sensors that make up the tape reader itself. Along the left edge there is a series of holes intended to act as a guide so you may punch your own tapes. On the back of the badge you’ll find the PIC16F15355.

The tape is fed through, with one hole in the center (smaller than the rest) serving as the clock signal. The other eight holes deliver the data.

The assembly technique for this badge is incredible. If you look along the edge you can see how the three panels rest on the carrier board. During fabrication some metal stock was used as a spacer to leave room for the paper tape to feed after the panel was reflowed — there are pads on the underside of the panel that mate with footprints on the carrier board.

I would be very expensive to manufacture this if you used a contract manufacturer. Luckily, the Toymakers are their own CM so they just splurged on custom processes by adding to their own labor. It’s really impressive to see the modular design and commitment to making this work. I like it that the depth of the carrier board helps to reduce how far the battery holder for the CR2450 coin cell sticks out.

Here are detailed views of the panels. The rear-mounted LEDs on the battery panel are red/green, and the LEDs on the semaphore panel are red only.

Tape pattern found in the conference program Tape pattern found on the back of the badge Machine used to punch the tape These rolls of paper tape are fairly rare now

The conference is called Cyphercon, so it’s not surprising there’s a puzzle to be solved. You find tape patterns on the back of the badge and in the conference guide book. Badges for presenters and organizers are different and I assume you need to collect all the patterns and assemble them to unlock what’s hidden within.

It’s a beautiful badge, even if you’re not trying to solve the badge puzzle. But the interactivity is so enticing. So far I’ve seen one team who brought a laser printer and transparencies to make their own tapes, leaving the “holes” unprinted on the strips. And another person mentioned trying to connect directly to the IR sensors with another microcontroller to electrically spoof feeding tape through it. It’s a simple mechanism, and a hit for everyone trying to solve the puzzles at this conference.

Here’s a video about the badge made by Toymaker’s to explain the activities involving this badge.