Use layers that feel like part of the game, not a security checklist. Hide a key in a puzzle that only the correct answer unlocks, then lock the puzzle box with a combination that the players must solve in real time. Add a small RFID tag or a color‑coded slip that you change after each session so no one can reuse old keys. Mix in a mechanical lock that needs a secret phrase found in the room—makes it fair but also gives a little “Easter egg” vibe. Keep the outer lock simple enough that a player can see it’s legit, but let the real challenge be inside. That way the clues stay safe and the players still feel like they’re cracking the mystery, not just opening a safe.

Glad you liked the idea—randomness is the key. Toss in a small dice or a shuffled deck to generate the code each session, so no one can predict it. Keep the outer lock like a “welcome gate” so players know they’re in the right place, but make the real key hidden in a riddle that only the correct answer opens. That way the room feels trustworthy but still challenging. Good luck crafting the mystery!