Pigpen Cipher: Decode the Freemason's Cipher

The pigpen cipher, also known as the Freemason’s cipher, is a substitution cipher that swaps every letter for a fragment of a grid: the symbol for each letter is the shape of the cell it sits in. There is no shifting and no keyword. Learn the layout once and you can read it on sight, which is exactly why eighteenth-century Masonic lodges trusted it with a century of records.

What is the pigpen cipher?

Write the alphabet into four frames: two tic-tac-toe grids and two crosses. A to I fill the first grid. J to R fill the second, and each of those cells carries a dot. S to V take the pockets of the first cross, W to Z the second, dotted again.

Your letter’s symbol is the walls around it. A sits in the top left corner of the first grid, so its mark is a corner: one wall below, one to the right. E sits dead centre, so its mark is a full box. N sits dead centre of the dotted grid, so its mark is the same box with a dot inside.

That is the whole machine. No arithmetic, no key phrase to remember, just geometry. The name comes from the picture: the grid pens the letters in like pigs.

How do you decode a pigpen cipher?

Three steps, and the first one is the only real work.

1. Draw the key. Two grids, two crosses, dots on the second of each. Fill in A to Z in order.
2. Read each symbol’s shape. Count the walls and check for the dot. A full box is E; a full box with a dot is N.
3. Match the shape to its cell and write the letter down.

Take the four symbols above. The first is a box missing its left wall, with a dot: middle left of the dotted grid, M. The second and third are full boxes, no dot: E, twice. The last is a chevron opening left: the left pocket of the first cross, T. MEET.

Once the key is in your head you stop translating and start reading. Most people get there inside an hour.

Why is it called the Freemason’s cipher?

Because Freemasonry used it and the name stuck. Eighteenth-century lodges kept their correspondence and their records in it, and enough Masonic documents survive in pigpen that the system still carries the fraternity’s name two centuries later.

They did not invent it. The occult philosopher Heinrich Cornelius Agrippa described a close cousin in the early 1500s: an arrangement of the alphabet into nine chambers whose walls stood in for the letters. The Freemasons took a good trick and gave it a reputation.

What they wanted from it was never secrecy in the military sense. Lodge records were not state papers, they were private business among members. Pigpen gave them a script any brother could read on sight and any outsider would find opaque at a glance. That is a low bar, and pigpen clears it perfectly.

Pigpen code, masonic cipher, tic-tac-toe cipher: are they the same thing?

Yes. Every one of those names points at the same grid.

The names differ by who is telling you about it. A puzzle book says pigpen. A history of the lodges says Freemason’s cipher. A classroom says tic-tac-toe. The chart above decodes all of them, because underneath the naming there is one alphabet dealt into four frames and nothing else.

The Rosicrucian name is the exception on that list. The brotherhood used pigpen-style ciphers too, but one seventeenth-century Rosicrucian system used a single grid of nine cells and marked the letter by where the dot sat inside it. The chart above will not open that one.

If a message resists the standard chart, the problem is not which name it goes by. It is that the writer used a different chart. The common variant deals the letters into the four frames in a different order. The rarer one abandons the four frames altogether.

Where can you still see the pigpen cipher?

Carved in stone, for one. In Trinity Church cemetery in New York, the headstone of James Leeson, who died in 1794, carries a strip of pigpen symbols above his name. It kept its secret for the better part of a century before anyone published a reading. Decoded, it says REMEMBER DEATH.

The cipher never retired after that. It passed into scouting handbooks, then into escape rooms, geocaches, and puzzle books, and it earns its place in all of them: it looks like sorcery and reads like the alphabet.

Is the pigpen cipher secure?

No, and it never was. Pigpen is a monoalphabetic substitution cipher: one symbol per letter, the same symbol every time. Dress the alphabet in geometry and the mathematics does not change. Count the symbols, and the most frequent one is almost certainly E. The one-symbol words are A or I. From there it unravels like any newspaper cryptogram, and the standard key is so well known that most of the time there is nothing to break at all.

That fragility is the lesson. A cipher that hides the shape of the letters, and not their pattern, falls to anyone with a pencil and patience. If you want the full toolkit, our guide to solving cryptograms walks the whole method: frequency counts, pattern words, and the footholds that open any substitution.