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 Note

The British detective's note in the Dancing Men cipher.

Playable Lupin: Lettre

Lupin's letter, acrostic decoy and a Baconian payload.

Playable Cabinet Noir, Bureau de Lecture

The routing slip entry point (Polybius square).

Download seal.png

The wax seal, a PNG with a hidden transcription slip (bonus tier).

Writeup Brief

Challenge prompt and objective, non-spoiler.

Writeup · spoiler Solution

Full author walkthrough and both flags.