Pigpen Cipher
The Freemason cipher — symbols instead of letters, used for centuries in secret societies
Symbol frequency analysis · Pattern recognition
Why This Matters
The Pigpen cipher — used by Freemasons from at least the 18th century — is one of the most widely recognized symbol ciphers in history. It demonstrates that substituting symbols for letters provides no additional security over substituting other letters.
Pigpen alphabets use geometric fragments and dots as letter symbols. Kahn records a concrete Masonic example on James Leeson’s 1794 gravestone in New York. Layouts vary: an inscription needs its own alphabet convention, rather than an assumed universal Masonic key.
A secret pigpen alphabet is a monoalphabetic substitution; symbols preserve the same repetition patterns as letter substitutes. A published fixed alphabet can instead be decoded by lookup. Caesar’s restricted shift family has a much smaller keyspace than a freely permuted substitution, so the two should not be assigned identical attack difficulty.
The grid layouts: A │ B │ C J │ K │ L ───┼───┼─── ───┼───┼─── D │ E │ F M │ N │ O (dotted versions) ───┼───┼─── ───┼───┼─── G │ H │ I P │ Q │ R S = ╲ T = ╳ U = ╱ (X shapes) V = ╲• W = ╳• X = ╱• (dotted X) Y = ▽ Z = △ (chevrons) The symbol for a letter is the set of grid lines that enclose its cell — nothing more: A = top-left cell → line on the right, line below E = centre cell → all four sides: a closed box H = bottom-middle → left, top and right: open below I = bottom-right → line above, line to the left ...etc — a dot marks the second grid (J–R) (The demo above prints single text characters as stand-ins, because plain text has no glyphs for most of these shapes. The diagram below shows this exhibit’s drawn variant; its S–Z assignment differs from the common four-wedges-per-X layout.) Documented example: - James Leeson’s Masonic gravestone, New York, 1794
A known alphabet needs only lookup. With an unknown alphabet, frequencies, repeated words and word shapes can support a substitution attack. The most frequent symbol is not necessarily E, and short inscriptions may be ambiguous. No universal minutes-to-recovery guarantee follows from using geometric symbols.
| Concept from Pigpen Cipher | Modern Evolution |
|---|---|
| Symbol substitution | Visual encoding: QR codes, barcodes use symbol-to-data mapping |
| Fixed symbol grid | Character encoding standards: ASCII, Unicode map characters to numbers |
| Secret society use | Need-to-know access control: modern cryptography enforces this mathematically |
| Exhibit | 32 of 172 |
| Era | 18th Century |
| Trust | Broken |
| Inventor | Freemasons (popularized) · Earlier origins unknown |
| Year | ~1700s |
| Key Type | Fixed symbol-to-letter grid |
| Broken By | Symbol frequency analysis · Pattern recognition |
Sources and Reading
David Kahn, The Codebreakers: The Comprehensive History of Secret Communication from Ancient Times to the Internet, revised edition (1996), Chapter 21, “Heterogeneous Impulses,” on symbol alphabets and James Leeson’s 1794 inscription. The drawn S–Z variant on this page and the four-wedge layout in the fraternal-tradition widget are explicitly different conventions.