Crypto · Stego · Pwn2Play 2026
The Baker Street Affair
Belle Époque, summer 1908. Two intercepted documents, Holmes and Lupin, two perspectives on the same theft. Reconcile the cipher chain for the primary flag, and recover the Cabinet Noir verdict hidden behind the wax seal for the bonus.
Challenge files
Open anything you like.
Playable
The case file (dossier)
The Bureau de Lecture cover, brief, reader notes, both documents, and the seal.
Playable Holmes: Case NoteThe British detective's note in the Dancing Men cipher.
Playable Lupin: LettreLupin's letter, acrostic decoy and a Baconian payload.
Playable Cabinet Noir, Bureau de LectureThe routing slip entry point (Polybius square).
Download seal.pngThe wax seal, a PNG with a hidden transcription slip (bonus tier).
Writeup BriefChallenge prompt and objective, non-spoiler.
Writeup · spoiler SolutionFull author walkthrough and both flags.