Pigpen Cipher — Bench tool
Published 8 Sep 2026 ·
Pigpen writes letters as fragments of a grid. Two tic-tac-toe frames and two X frames give exactly 26 cells, so the cipher fits the alphabet perfectly with nothing left over — which is either elegance or coincidence depending on how you feel about such things. It was the standard private hand of eighteenth-century Masonic lodges and appears carved on gravestones and marked on charts.
- Era
- Medieval
- Type
- Substitution
- Key space
- 1 key (26 glyphs)
- Level
- Starter
IWhat this tool does
Draw four frames. The first two are tic-tac-toe boards; the last two are boxes with a diagonal cross. Each frame has nine cells, except the crossed ones which have four.
| Frame | Cells | Letters |
|---|---|---|
| north grid | 9 | A B C D E F G H I |
| south grid | 9 | J K L M N O P Q R |
| east cross | 4 | S T U V |
| west cross | 4 | W X Y Z |
So the letter C is the top-right cell of the north grid and the letter T is the top-right cell of the east cross. A dot inside a cell distinguishes the second family from the first, which is how the technique smuggles 26 distinct symbols out of 26 cells.
This bench writes those addresses in plain tokens — N1 is north-grid cell one, E3 is the third cell of the east cross — so you can see the mapping without drawing anything.
The important observation: the symbols are not arbitrary squiggles. They have a geometry, and geometry can be read.
IIThe key
There is no key. The glyph set is fixed and public, and has been printed in scout manuals for a century.
The apparent cleverness is that 9 + 9 + 4 + 4 = 26 exactly. That arithmetic is the entire design, and it is also the entire problem: because every letter is a shape, and shapes have neighbours.
A substitution cipher whose alphabet is printed on a poster cannot be protected by secrecy. It can only be protected by being hard to read by eye — and pigpen is not.
The dot convention is worth noting as a design pattern: it is the same trick as the Caesar shift, applied to a visual alphabet instead of a letter alphabet. When you run out of cells, add a mark.
IIIWhat it will not protect
Historical ciphers are for study and recreation and are not suitable for protecting real information. The full analysis is in the cipher entry.
Read the full entry, with deciphering steps and weakness analysis →