Sword of Secrets is a multi-stage hardware Capture the Flag (CtF) challenge designed for hackers, tinkerers, and puzzle lovers who crave hands-on problem-solving. Housed in a sleek, keychain-sized board, this open-source adventure weaves together hardware hacking, cryptographic trickery, and low-level exploitation. As you delve through the stages, your mastery of embedded systems, RISC-V assembly code, datasheets, and creative debugging will be tested. Solving it means digging into both the schematics and the source code—and truly understanding them.

This is more than a test of your technical prowess—it’s a full-blown embedded gauntlet. A spiritual successor to Uri Shaked’s The Skull CTF, Sword of Secrets dares you to challenge how security is done—and undone—at the hardware level. Each stage unearths a new exploit path through cryptographic missteps, embedded assumptions, and silicon secrets. You’ll breach protection registers, twist SPI protocols, and bend memory layouts to your will—sometimes through the backdoor. With UART as your guide and datasheets as your map, this isn’t just a board—it’s an offensive security saga disguised as a keychain.

Flex Your Hardware, Cryptography, and Embedded Exploitation Skills

Sword of Secrets begins with hands-on hardware exploration. Review schematics, trace signal paths, and study datasheets to understand how the system works. Many challenges rely on spotting subtle design choices and using that knowledge to uncover hidden functionality or bypass protections.

You’ll face cryptographic challenges inspired by real-world exploits. The tasks focus on identifying flawed assumptions and implementation issues, requiring a solid understanding of how cryptography can fail in practice, not just in theory.

SoS uses a RISC-V microcontroller, and many challenges involve working at the firmware level. You’ll interact with low-level code and hardware interfaces, using precise control of execution to reveal vulnerabilities and gain deeper system access.

New Challenges Released on a Regular Schedule

Sword of Secrets supports online updates over USB, making it easy to flash new content without additional hardware. Each update adds a new stage or puzzle, expanding the challenge over time. We will publish new riddles on a regular schedule for at least the first year after fulfillment is complete. So, even after you’ve solved the initial stages, you will still have something new to explore, exploit, or reverse-engineer.

These updates aren’t just plain binaries—they’re encrypted using a key embedded deep inside the microcontroller, protected by on-chip safeguards. In theory, this means the riddles can only be decrypted and executed by the device itself. If you think you can extract the key, bypass the protection, or decrypt the firmware off-device, we dare you to try it.

Sword Unlocked

Sword of Secrets comes with a locked bootloader by default—only officially encrypted firmware can be flashed to preserve the mystery. However, we invite you to unlock its true potential! As a stretch goal, we’re releasing an open bootloader version, transforming the device into a fully hackable platform. With it, you’ll be able to forge and flash your own adventures, share quests with fellow seekers online, and join a growing community of creators, tinkerers, and heroes crafting legends of their own.

Features & Specifications

• Microcontroller: CH32V003 32-bit RISC-V
• Storage: W29Q128 serial NOR flash
• USB Controller: CH340E

Comparisons

Documentation & Support

The hardware schematics and design are completely open source and freely available for replication. All software (minus the cryptographic keys 😉) can be found in our GitHub repository. The KiCad project will be available from launch day, allowing anyone to recreate the hardware with ease. The software can be flashed using any compatible WCH flashing tool. And for those of you that cannot wait, you can find a virtual preview to whet your appetite.

Manufacturing Plan

Several fully working prototypes of Sword of Secrets have already been manufactured and thoroughly tested. During the prototyping phase, multiple manufacturing partners in China were evaluated, with one selected based on consistent build quality, communication, and the ability to scale production. The prototypes have also undergone laboratory testing for RoHS and EMC compliance to meet CE and UKCA certification standards. The manufacturing partner we chose is PCBWay. They offer a wonderful PCB-fabrication service and have helped me a lot with the certification process.

Once the crowdfunding campaign concludes and production quantities are confirmed, the final manufacturing run will begin. All completed units will be shipped to Israel for firmware flashing, followed by a full quality-control process. Each device will be individually inspected and tested to ensure functionality, reliability, and consistency. Only after passing this inspection and validation stage will the devices be shipped to the United States for final distribution.

Fulfillment & Logistics

After our production run is complete, we will package everything up and send it along to Crowd Supply’s fulfillment partner, Mouser Electronics, who will handle distribution to backers worldwide. You can learn more about Crowd Supply’s fulfillment service under Ordering, Paying, and Shipping in their guide.

Risks & Challenges

As with any hardware project, there are inherent risks and challenges that may arise during manufacturing. These include potential issues such as production defects, yield variability, and mistakes during fabrication and assembly—especially with high-precision elements like the USB edge connector. While the global supply chain has largely stabilized, the possibility of unexpected IC shortages or sourcing delays, though unlikely, cannot be fully ruled out. Firmware-related bugs or unforeseen edge cases may also emerge, particularly as the project is designed to support a wide range of user interactions and challenge logic.

To mitigate these risks, every device will undergo manual inspection, firmware flashing, and functional testing as part of a comprehensive quality control process before being packaged for delivery. On the software side, Sword of Secrets includes an update mechanism that enables secure firmware updates at any time, ensuring bugs or improvements can be addressed remotely, even after distribution. Additionally, the full software stack is open-source, allowing the community to contribute, audit, or suggest changes. Feedback and collaboration are both encouraged, forming a robust foundation for long-term support and improvement.