The Skull CTF

A mind-bending hardware puzzle in three acts

Feb 10, 2021

Project update 15 of 18

A Perilous Crossing

by Uri Shaked

Ahoy Mateys!

五百九十六 %

The Other End of The Ocean

Your Skulls have made it to the other end of the ocean! We managed to sneak them out of China just before the Lunar New Year, and the Deadly-Hook Looters have delivered them safely to Crowd Supply’s logistics department…whose enforcers then threatened to incinerate the entire shipment unless we posted the following update:

Please Update Your Shipping Address

Skulls will begin shipping soon, so please take some time to check your Crowd Supply account and make sure that your shipping address is up-to-date. By doing so, you will help Crowd Supply avoid delays. Once they have sent your order details to their warehouse team for processing, it may be impossible for them to re-route your shipment. If you have fulfillment-related questions or concerns, please contact Crowd Supply Support.

A Race to the Top

When you receive your Skull, you’ll have two choices: you can sit there and stare at her—we’ve done thorough validation testing to ensure that she will stare back at you—or you can play the game and try to claw your way into our Top 10 List!

Here’s how the scoring works: each challenge has a base score, and your final score is calculated by adding a rank bonus and a brevity bonus to that base score:

Final score = base score + rank bonus + brevity bonus

Base Scores

The base scores are:

ChallengeBase scoreBytes **
Capture The Flag4500-
Mind Control950039
The Virus *7500130
Medulla Oblongata *750089

* These are the bonus challenges
** The Bytes value is used for the brevity bonus and will be explained below.

Rank Bonuses

Your rank bonus will depend on how many people have already solved that particular challenge:

RankRank bonus

Brevity Bonuses

Your brevity bonus works as follows: if the size of your solution (in bytes) is smaller than the value in the Bytes column above, then you get 100 additional points for each byte you saved. But if your solution is larger than that value, then you lose 50 points for each extra byte.

An Example

Suppose you were the 2nd person to solve the Mind Control challenge, and your solution was 40 bytes long. In this case, your score would be calculated as follows:


You can submit an improved solution at any time. If you do, a second score will be calculated based on the number of solutions that have been submitted at that point in time. Your actual score will only change if this new score is higher than your previous one.

A Recap of the Rules

  1. No hardware modifications!
  2. Your solution shouldn't use any kind of electrical connection to the skull.
  3. The solution has to be reproducible, and you have to be able to explain how it works.

Send your solutions to uri+skull at wokwi dot com

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