The Skull CTF

by Wokwi

A mind-bending hardware puzzle in three acts

View all updates Dec 07, 2020

Answers Begin to Manifest...

by Uri Shaked

Ahoy Mateys!

The 48th Prime Number%

Today, we took our entire team of Skulls to a resort so they could relax and prepare for the final week of the campaign!

As soon as we got back, however, we received a phone call from the CEO of Crowd Supply, and he was not happy. Apparently, we forgot to include the invite link for Wednesday’s AMA in our previous update. Once we got him calmed down, we swore that we’d include the link in this update, and he said he’d "let it slide. This time." So here you go:


We also want to thank @YoavW for discovering the secret in her eyes! But don’t worry, the challenge is still open for the rest of you. If you figure it out, simply send us a SHA-256 hash of the following three items: the solution, a space character, and your Twitter username (e.g. echo -n "solution mytwitter" | sha256sum). Sorry about the extra hassle. Our shaman recently warned us that, "to avoid a disastrous outcome," we must NEVER send the solution in cleartext…

About the Author

Uri Shaked


$3,298 raised

of $666 goal

495% Funded! Order Below

Product Choices


The Skull

A single The Skull CTF board (☠)


SparkFun Programmer

From the Crowd Supply Basics project.

Design your own puzzles and load them into The Skull's brain using this programmer! Mini USB cable not included.

AVR Pocket Programmer by SparkFun


EconoStik Header: DR VT SMT 2x3

From the Crowd Supply Basics project.

Use with the SparkFun Programmer.

One Amphenol FCI EconoStik™ 2.54mm Header. SMD/SMT Mounting style, Straight angled male pins, gold-plating. Voltage rating: 110 V



Wokwi creates tools for the Arduino and maker community, such as AVR8js, the Open source Arduino Simulator, and GoodArduinoCode.

Uri Shaked

JA Electronics


PCB Fabrication & PCB Assembly

See Also

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