Unit 7 · Codebreakers

Picture a farm. Pigs live in small fenced areas called pens. The pigpen cipher gets its name from that idea. Each letter of the alphabet lives in its own little pen. To write a letter in code, you draw the shape of its pen instead of the letter.

Here is one common way to set it up. Draw a tic-tac-toe grid and put A through I in its nine spaces. Draw a second grid with a dot in each space for J through R. Then draw a big X for S, T, U and V. A second X with dots holds W, X, Y and Z.

Now look at the letter A. It sits in the top left corner of the first grid. Its pen has a line on the right and a line on the bottom. So A is written as a shape like a backward L. Every letter gets a shape this way. There are other versions of the key, so the letters may sit in a different order.

Many people say the Freemasons invented pigpen. The Freemasons are a brotherhood that began with stonemasons, the workers who built with stone. Their lodges, or clubs, grew in Britain in the 1600s and 1700s. But the idea of hiding letters in a grid is older than their lodges.

In the 1530s, a German writer named Heinrich Cornelius Agrippa published a big book about hidden knowledge. Scholars agree it shows letters placed in a grid of boxes. Historians see this grid as an early ancestor of pigpen. That book came out long before the first grand lodge of Freemasons.

So the Freemasons did not invent the grid. They took it up and spread it. Masons used it widely from the 1700s. That is why pigpen is also called the Masonic cipher or the Freemasons’ cipher. A name can tell you who used a thing most, not who made it first.

People often say "code" for any secret message. Codebreakers use two words. A code swaps a whole word or idea for something else. For example, a team might agree that "pizza" means "meet at the gym." You need the list of meanings to understand it.

A cipher works on single letters. Each letter is changed into another letter or a symbol. Pigpen is a cipher, because every letter gets its own shape. You can hide any word with a cipher, even a word nobody planned for.

The message you start with is called plaintext. It is the plain words anyone can read. After you hide it, it is called ciphertext. Changing plaintext into ciphertext is called enciphering. Changing it back is called deciphering. Many people also say encode and decode.

Trinity Church stands on Broadway at Wall Street in Lower Manhattan. Around it is an old churchyard, a burial ground next to a church. People have been buried there since the 1600s. Today it sits among tall office buildings.

One stone belongs to James Leeson, who died in 1794. The stone shows a square and a compass. That is a well-known symbol of the Freemasons. It tells us Leeson was likely a Mason, or his friends wanted to honor the Masons. The stone also has other carvings often seen on old graves.

Across the stone runs a line of small shapes. They are letters in the pigpen cipher. Anyone who knows the key can read them. Many visitors walk right past without noticing. That is part of what makes it a good mystery for a codebreaker.

When you decode the shapes on the Leeson stone, they spell REMEMBER DEATH. You can check this yourself. Match each shape to its pen in the key. The letters line up one by one. Many writers and codebreakers have checked it the same way.

The words may sound gloomy at first. But they were a very common message in those days. People called this kind of reminder by a Latin name, memento mori. It means "remember that you will die." The idea was to live well, be kind and use your time wisely.

Old gravestones in Europe and America often carried this message. Some showed an hourglass, with sand running out. Leeson’s stone says the same thing in a quieter way. Only people who knew the cipher could read it at a glance.

A gravestone is public. Anyone can walk by and look. So why carve words that most people cannot read? We do not have a letter from Leeson or his friends that explains it. Historians can only look at the clues.

One clue is the square and compass. Masons in the 1700s knew the pigpen cipher well. A line in pigpen could be a quiet message to fellow Masons. It said, in effect, "This man was one of us." It was a way of belonging, like a team handshake.

Some people online claim the stone hides a treasure map. There is no evidence for that. The decoded words are a common saying about life and death. When a message is solved, it is wise to trust what the letters say. A good historian asks for evidence before believing an exciting story.

To substitute means to put one thing in place of another. A substitution cipher puts a new letter or symbol in place of each letter. Pigpen is a substitution cipher. Each letter is always swapped for the same shape.

A very old example comes from ancient Rome. The Roman writer Suetonius wrote about the life of Julius Caesar. He said Caesar sent private letters in a cipher. Each letter was moved a few places down the alphabet. Today this is called a shift cipher, or the Caesar cipher.

Here is how a shift of three works. A becomes D. B becomes E. C becomes F. So the word CAT becomes FDW. To read it, you shift each letter back three places. The rule is simple, and it stays the same for the whole message.

Think of a locked diary. The lock keeps the pages private. The key opens it. A cipher works the same way. The key is the rule or chart that hides the message and brings it back.

For a shift cipher, the key is a number, like three. For pigpen, the key is the drawing of the grids and X shapes. The person sending the message and the person getting it both need the same key. Anyone else should not have it.

Here is a problem. The pigpen key has been printed in many books. Today almost anyone can find it. So pigpen hides a message only from people who have not learned it. A cipher is only as strong as the secret of its key.

More than 1,100 years ago, a scholar named al-Kindi lived in Baghdad. He wrote the oldest known guide to breaking ciphers. His big idea was to count. In any long piece of writing, some letters show up much more than others.

In English, the most common letter is E. Codebreakers measure it at about 12.7 out of every 100 letters. Next come T, A and O. Letters like Q and Z are rare. Counting how often each letter appears is called frequency analysis. Frequency means how often something happens.

Here is how it helps. Say a secret message uses the shape of a triangle more than any other symbol. That triangle probably stands for E. The codebreaker writes E above each triangle. One guess at a time, the message starts to open.

Counting letters is a great start, but it is not the whole job. Short messages can trick you. In REMEMBER DEATH, E is most common, which fits. But a short note about a zoo might have lots of Z and O. So codebreakers look for more clues.

Short words are strong clues. In English, a one-letter word is almost always A or I. A common three-letter word is THE. If a message has the same three symbols again and again, they may spell THE. Then you know T, H and E all at once.

Codebreakers also look for patterns. A double symbol, like in the middle of LOOK or BALL, is often O, E, L, S or T. Each guess is tested against the whole message. If a guess makes real words, keep it. If not, try again. Mistakes are part of the work.

Now it is your turn. Your class can split into two teams. Team One makes a message. They choose a short sentence, maybe ten to fifteen words. They pick a cipher, such as a shift cipher or their own symbol alphabet. They keep the key hidden.

Team Two gets only the ciphertext. First, they count each symbol and make a tally chart. Next, they look for one-letter words and repeating groups. One person can track guesses on the board. Another can read the message aloud as it changes.

Real codebreakers work in teams too. One person may be good at counting. Another may notice patterns or know many words. When the message is solved, both teams can talk. What made it hard? What gave it away? Teamwork makes both sides stronger.

The Copiale Cipher is a real book. It has 105 handwritten pages. Its cover is made of green and gold patterned paper. Experts at Stockholm University say it was written around 1730. That makes it almost 300 years old.

The book holds about 75,000 written characters. A character is any single mark, like a letter or a symbol. The writer used about 90 different symbols. Some are ordinary letters from the Roman alphabet. Others are made-up shapes.

Think about that number. English has only 26 letters. So why would a writer need about 90 symbols? That big number was one of the first clues. It told the researchers that this was not a simple swap of one letter for one symbol.

When people first saw the Copiale, the Roman letters looked like the best place to start. They look like normal writing. But the researchers found they were mostly a trick. The team reported that the plain letters mostly served as spaces or decoys. A decoy is something meant to fool you.

The real message was hidden in the strange symbols and in letters with little marks above them. That is where the German words were. Readers who studied only the plain letters were looking in the wrong place.

The writer used one more trick. Common letters, like E, had several different symbols. This is called a homophonic cipher. It makes letter counting harder. If E is split among four symbols, no single symbol stands out as the most common one.

Old books can sit on shelves for a very long time. The Copiale was written around 1730. It was cracked in 2011. That is a gap of almost 300 years. During that time, nobody we know of could read it.

A timeline helps you see a gap like that. Put the years in order on a line. Then you can compare them. For example, the Leeson stone in New York was carved around 1794. That is about 60 years after the Copiale was written.

Our timeline also shows an older event. In 1599, a Scottish official named William Schaw wrote rules for stonemasons. You will read about those rules later in this chapter. They asked masons to be tested on their memory.

Kevin Knight studies how computers work with human languages. For the Copiale, he first had the symbols typed into a computer. Each symbol got a name so the computer could track it. That took careful work by people.

Then the computer could do what it does best. It counted every symbol in seconds. It found which symbols came together often. It compared those patterns with patterns in many real languages. A person counting 75,000 characters by hand would need a very long time.

The team’s work pointed to German as the hidden language. But the computer did not understand German. It only matched patterns. People still had to test each guess and make sense of the words. A computer is a powerful tool, but it needs a thinking person to guide it.

As German words began to appear, Beáta Megyesi noticed something. One symbol seemed to stand for a whole word: "eye." In German that word is Auge. The word eye seemed to come up again and again.

Why would a book care so much about eyes? Christiane Schaefer found the link. She connected the book to a secret society called the Oculists. The name comes from a Latin word for eye. It is also the root of the English word ocular, which means about the eyes.

That one small word opened the whole book. Once the team knew the subject, other words made sense. In 2011 they shared how they did it in a paper for other scientists. Many news reporters around the world told the story.

Each person on the Copiale team brought something different. Knight knew how to make computers find patterns. Megyesi knew languages and how to study them with computers. Schaefer studies old languages and their history.

No one of them had every skill. Together, they did. This happens often in science and history. Big puzzles get solved when people share what they know. It is called collaboration, which means working together toward one goal.

Think about your own strengths. Maybe you notice tiny details. Maybe you remember words well. Maybe you stay calm when a puzzle is hard. Every one of those strengths helps a codebreaking team. Asking for help is also a skill.

The decoded Copiale describes the ceremonies of the Oculists. A ceremony is a set of actions done in a special order for an important event. Many of these were for bringing in new members. The ceremonies were built around eyes and seeing.

Some summaries say the Oculists were a club of eye doctors. The researchers read it differently. They saw the eye as a symbol. To "see" meant to learn and understand the truth. People still talk this way. We say "I see" when we mean "I understand."

The Oculists seem to have been like the Freemasons in some ways. They met in secret, used symbols and had steps for joining. There were many clubs like this in Europe in the 1700s. The Copiale gives us a rare look inside one of them.

Before it was cracked, people could imagine anything about the Copiale. A hidden plot? A treasure? A dark crime? Secret books make people wonder. But when the words were read, they described ceremonies and lessons for members.

Members of groups like the Oculists had their own reasons for secrecy. The ceremonies felt special because they were private. New members did not know what was coming. That made the moment of joining feel important. Secrecy also helped members trust one another.

Outsiders often saw it another way. In the 1700s, some critics feared that secret clubs hid plots against rulers or churches. Those fears were real feelings. But in this case, the evidence shows the secret protected a ceremony. Historians let the evidence decide.

William Schaw was the Master of Works for King James VI of Scotland. That means he was in charge of the king’s buildings. He also wrote rules for the lodges of stonemasons. These rules are called the Schaw Statutes. A statute is a written rule.

The first set came in December 1598. A second set followed in December 1599. One part spoke to the lodge at Kilwinning, a town in Scotland. It said the lodge leaders must test every skilled mason and every apprentice on "the art of memory." An apprentice is a person learning a trade.

The old Scots words say "airt of memorie." The rules even set a fine, a money penalty, for a mason who forgot. Why would builders be tested on memory? Masons had to keep a lot in their heads. They needed building skills. They also needed the rules and words of their lodge.

An old story comes from ancient Greece. The Roman writer Cicero told it. A poet named Simonides was at a big dinner. He stepped outside, and the roof of the hall fell in. Simonides could name every guest by remembering where each one had sat. It is told as a legend, and it gave people an idea.

The idea is called a memory palace. You picture a place you know well, like your home. Then you "put" each thing you need to remember in a spot along the way. To remember, you take a walk in your mind. You find each thing where you left it.

What did Schaw mean by the art of memory? Historian David Stevenson thinks it may mean memory methods like this one. They were popular in Schaw’s time. Other historians are not sure how far to take this idea. The rules do not explain the words, so the question stays open.

Codes and memory worked together for Masons. Masons were expected to learn their ceremonies by heart. That is a lot of words to remember. So some kept small books to help them study.

The Scottish Rite Masonic Museum and Library in Lexington, Massachusetts, keeps several of these books. One is a pocket-size notebook in cipher. Another is a whole ceremony book in cipher from about 1920. Masons saw them as private study helps. Critics saw them as proof of hidden secrets.

You can use both tools too. Try a memory palace for spelling words or science facts. Or make a small study card in your own cipher. Everyone learns in their own way. Pictures, places, codes and practice can all help your brain hold on to ideas.