Crypto Wiki
File:Pigpen cipher key.svg

The pigpen cipher uses graphical symbols assigned according to a key similar to the above diagram.[1]

The pigpen cipher (sometimes referred to as the masonic cipher, Freemason's cipher, or Rosicrucian cipher)[2][3] is a geometric simple substitution cipher which exchanges letters for symbols which are fragments of a grid. The example key shows one way the letters can be assigned to the grid.


The use of symbols is no impediment to cryptanalysis, and this system is identical to that of other simple monoalphabetic substitution schemes. Due to the simplicity of the cipher, it is often included in children's books on ciphers and secret writing.[4]


The exact origin of the cipher is uncertain,[5] but records of this system have been found which go back to at least the 18th century. Variations of this cipher were used by both the Rosicrucian brotherhood[5] and the Freemasons, though the latter used it so often that the system is frequently called the Freemason's cipher. They began using it in the early 18th century to keep their records of history and rites private, and for correspondence between lodge leaders.[3][6][7] Tombstones of Freemasons can also be found, which use the system as part of the engravings. One of the earliest stones in Trinity Church Cemetery in New York City, which opened in 1697, contains a cipher of this type which deciphers to "Remember death". George Washington's army had documentation about the system, with a much more randomized form of the alphabet. And during the American Civil War, the system was used by Union prisoners in Confederate prisons.[5]


The core elements of this system are the grid and dots. Some systems use the X's, but even these can be rearranged. One commonly used method orders the symbols as shown in the above image, ##XX. Another commonly used system orders the symbols as #X#X. Another is ###, with each cell having a letter of the alphabet, and the last one having an "&" character. Letters from the first "#" have no dot, letters from the second each have one dot, and letters from the third each have two dots. Another variation of this last one is called the Newark Cipher, which instead of dots uses one to three short lines which may be projecting in any length or orientation. This gives the illusion of a larger number of different characters than actually exist.[8]

r system, used by the , used a single "#" grid of nine cells, and 1 to 3 dots in each cell or "pen". So ABC would be in the top left pen, followed by DEF and GHI on the first line, then groups of JKL MNO PQR on the second, and STU VWX YZ on the third.[2][5] When enciphered, the location of the dot in each symbol (left, center, or right), would indicate which letter in that pen was represented.[1][5] More difficult systems use a non-standard form of the alphabet, such as writing it backwards in the grid, up and down in the columns,[4] or a completely randomized set of letters.


Using the example key in the above image, the message "X marks the spot" is rendered in ciphertext as:

In popular culture[]

File:Ac2 cipher key.png

Variation of the Freemason cipher used in the computer game Assassin's Creed II

The Pigpen cipher has been used in several works of popular culture including Dan Brown's 2009 novel The Lost Symbol, both in the book itself, and also to provide a puzzle in the artwork of the U.S. version of the bookjacket. The Trap, a 2009 nominee for Lancashire Children's Book of the Year, uses a variation of the Pigpen cipher.[9]

In the computer game Assassin's Creed II, the cipher is used in the hidden glyph puzzle number 10, titled "Apollo". Here the cipher is one of many hidden messages tucked away in paintings and photos of historic events or people. Though not essential to the play of the game, the encrypted messages, some of which also use Morse Code and binary code, provide clues to the game's back-story.

The cipher is also the key to solving the third secret message found on the fictional website of Sherlock Holmes entitled "The Science of Deduction", created to accompany the BBC series Sherlock. It is presumably meant to have been left by Moriarty.


  1. 1.0 1.1 Wrixon, pp. 182–183
  2. 2.0 2.1 Barker, p. 40
  3. 3.0 3.1 Wrixon, p. 27
  4. 4.0 4.1 Gardner
  5. 5.0 5.1 5.2 5.3 5.4 Pratt, pp. 142–143
  6. Kahn, 1967, p.~772
  7. Newton, 1998, p. 113
  8. Glossary of Cryptography
  9. Template:Cite book


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External links[]

ca:Xifrat dels francmaçons de:Freimaurer-Alphabet es:Cifrado francmasón eo:Ĉifro de Framasonismo fr:Chiffre des Francs-maçons it:Cifrario pigpen nl:Rozenkruisersgeheimschrift pt:Cifra maçónica sv:Murarchiffer zh:豬圈密碼