Developer Builds Local AI Tool That Writes and Verifies CTF Reverse-Engineering Challenges

A developer created SlothCTF, an open-source tool that uses a locally run open-weight model to generate reverse-engineering CTF challenges from a short text prompt. Early attempts failed because language models repeatedly miscalculated byte-level XOR encoding, so the design was changed to have the model write C programs while the compiler performs the exact arithmetic. Each generated challenge is compiled, executed, and checked to confirm the flag is recoverable, that correct input is accepted and wrong input rejected, and that the plaintext secret does not appear in the binary's strings. The developer reported that all 20 of their planned challenge prompts produced valid challenges, each including source code, a compiled binary, a player README, and an organizer walkthrough. The project was submitted to a Hacktoberfest open-source AI challenge.