The pigpen cipher 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.

Security

The use of symbols is no impediment to cryptanalysis

Cryptanalysis

Cryptanalysis is the study of methods for obtaining the meaning of encrypted information, without access to the secret information that is normally required to do so. Typically, this involves knowing how the system works and finding a secret key...

, 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.

History

The exact origin of the cipher is uncertain, 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 and the Freemasons

Freemasonry

Freemasonry is a fraternal organisation that arose from obscure origins in the late 16th to early 17th century. Freemasonry now exists in various forms all over the world, with a membership estimated at around six million, including approximately 150,000 under the jurisdictions of the Grand Lodge...

, 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. 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

Trinity Church Cemetery

Trinity Church Cemetery consists of three separate burial grounds associated with Trinity Church in Manhattan, New York, USA. The first was established in the Churchyard located at 74 Trinity Place at Wall Street and Broadway...

 in New York City

New York City

New York is the most populous city in the United States and the center of the New York Metropolitan Area, one of the most populous metropolitan areas in the world. New York exerts a significant impact upon global commerce, finance, media, art, fashion, research, technology, education, and...

, which opened in 1697, contains a cipher of this type which deciphers to "Remember death". George Washington

George Washington

George Washington was the dominant military and political leader of the new United States of America from 1775 to 1799. He led the American victory over Great Britain in the American Revolutionary War as commander-in-chief of the Continental Army from 1775 to 1783, and presided over the writing of...

's army had documentation about the system, with a much more randomized form of the alphabet. And during the American Civil War

American Civil War

The American Civil War was a civil war fought in the United States of America. In response to the election of Abraham Lincoln as President of the United States, 11 southern slave states declared their secession from the United States and formed the Confederate States of America ; the other 25...

, the system was used by Union

Union (American Civil War)

During the American Civil War, the Union was a name used to refer to the federal government of the United States, which was supported by the twenty free states and five border slave states. It was opposed by 11 southern slave states that had declared a secession to join together to form the...

 prisoners in Confederate

Confederate States of America

The Confederate States of America was a government set up from 1861 to 1865 by 11 Southern slave states of the United States of America that had declared their secession from the U.S...

 prisons.

Variants

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: grid, grid, X, X. Another commonly used system orders the symbols as grid, X, grid, X. Another is grid, grid, grid, with each cell having a letter of the alphabet, and the last one having an "&" character. Letters from the first grid 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.

Another system, used by the Rosicrucians, 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. When enciphered, the location of the dot in each symbol (left, center, or right), would indicate which letter in that pen was represented. 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, or a completely randomized set of letters.

Example

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

In popular culture

The Pigpen cipher has been used in several works of popular culture including Dan Brown

Dan Brown

Dan Brown is an American author of thriller fiction, best known for the 2003 bestselling novel, The Da Vinci Code. Brown's novels, which are treasure hunts set in a 24-hour time period, feature the recurring themes of cryptography, keys, symbols, codes, and conspiracy theories...

'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

Lancashire Children's Book of the Year

The Lancashire Children's Book of the Year is an award given to works of children's literature, voted for by a panel of young judges. It was established in 1986 with the first award presented the following year...

, uses a variation of the Pigpen cipher.

In the game Assassin's Creed II

Assassin's Creed II

Assassin's Creed II is a historical third-person action-adventure video game developed by Ubisoft Montreal and published by Ubisoft for PlayStation 3, Xbox 360, Microsoft Windows and Mac OS X. It is the second video game installment of the Assassin's Creed series, and is a sequel to the 2007 video...

, 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

Morse code

Morse code is a method of transmitting textual information as a series of on-off tones, lights, or clicks that can be directly understood by a skilled listener or observer without special equipment...

 and binary code

Binary code

A binary code is a way of representing text or computer processor instructions by the use of the binary number system's two-binary digits 0 and 1. This is accomplished by assigning a bit string to each particular symbol or instruction...

, provide clues to the game's back-story

Back-story

A back-story, background story, or backstory is the literary device of a narrative chronologically earlier than, and related to, a narrative of primary interest. Generally, it is the history of characters or other elements that underlie the situation existing at the main narrative's start...

.

The BBC series, Sherlock, has created a website to correlate with the events in the series - The Science of Deduction. Under the "Hidden Messages" tab, "Sherlock" lists three coded messages he received from a stalker, and the third is in pigeon cipher.

In Club Penguin, a modified pigpen cipher is used for "Secret Agents".

External links

• The Elian Script is a similar grid-based cipher, used as art.
• Online Pigpen cipher tool for enciphering small messages.
• Cipher Code True Type Font
• FF Text Converter converts text in pigpen cipher and more.