Codes in larps


larpX has an article about using codes in larp, including “A note on ciphers” from a game called All For One:

(TL;DR: use caeser cipher for stuff you want trivially cracked or just to hide information from view; use Vigenere for stuff you want people to work at; give people keys and methods if you want them to just spend time).

While I didn’t play Musketeers, I wrote up a Guide to the Protection of Secrets for it, as a short guide to the codes of the era (I have no idea if Anna ever used it). I didn’t cover Vigenere or Nomenclaturs (number-based codes) as being too difficult. But it does have a few period steganographic methods used to conceal messages.

Musketeerscodes.pdf (63.5 KB)


I don’t think I’d ever put the Vigenere cipher in a game, myself - I know that they’ve been used and cracked in larp, but based on what I know about cryptography, there are two problems with employing them in larp:

  1. They were originally designed to be uncrackable, which means that your players need to break their backs working on it, and
  2. It’s only sensible to have your players break their backs if the encryption could only be a Vigenere cipher.

If the code is anything other than a Vigenere cipher, and the players spend time working on it assuming it’s a Vigenere cipher, that’s only going to be frustrating for them when they don’t get the answer. But if you tell them it’s a Vigenere cipher, then once they have the key the decryption is just busywork - there’s no actual puzzling involved.
The Caesar cipher is fine for hiding information from view: like any substitution cipher; they’re pretty easy to crack, especially if the plaintext includes words like A, I, THE, THAT, WHAT, etc.

I feel like the best larp-solving experiences come from something somewhere in between. Book ciphers and puzzle ciphers are great for this, because the encrypted text looks unusual in a way that could lead players to the encryption method - most book cipher text comes in a page-number.line-number.word-number form, like 23.11.6.

The first large-scale encryption I was involved with in a game was four pages of substitution cipher, with the twist that capital letters were encoded with different symbols than their lower-case counterparts. This injected some challenge back into solving.

If people want to use encryptions in game, I feel like there are two things they can do to make the experience evenly challenging for players:

  1. Provide a list of the cipher types you’ll use in the game (as was done for Musketeers)
  2. Vary the plaintext so that the ciphertext becomes harder to crack - if you reverse the plaintext before encoding, than the words A and I remain easy to crack, but everything else becomes a little more confusing. Same goes for if you stick an X somewhere in each word, or use a plaintext that has no Ts in it.

TL;DR: Encryption is hard to use effectively because it’s usually either impossible or trivial. If you want something in between, playing with the plaintext is a good place to start.


I used both Caeser and Vigenere in The Gehenna Memo, but as a representation of something else (translation and magical research respectively). In both cases, the key was known, and the use of a cipher was really a way of getting the players to spend time to uncover a rewarding text. It could equally have been sudoku, but ciphers seemed more diagetic.

(If I ever write His Majesty’s Wizards, the Tudor Laundry larp, I’ll have to use magic squares or something…)