Welcome, codebreakers!
A cipher is a secret way of writing. People have used them for thousands of years to send messages that only friends can read. In this class you will learn six codes, crack puzzles with each one, and then use everything to solve a real mystery.
How to earn your stamps
My codebreaker passport
0 of 7 stamps
The Case of the Golden Scarab
Something has gone missing from Mr. Lehmkuhl's desk. Six coded clues are waiting for you.
Binary Code
The secret language of computers: only 0s and 1s.
How it works
Computers only understand two things: off (0) and on (1). Think of a row of light switches. Each switch has a value. When a switch is on, you add its value.
With 5 switches, the values from left to right are 16, 8, 4, 2, 1. Add up the switches that are ON to get a number. Then turn the number into a letter: A = 1, B = 2, C = 3, all the way to Z = 26.
Fun fact: every photo, game, and video on a computer is stored as billions of 0s and 1s.
Example: decoding "HI"
The secret message is HI!
Try it: flip the switches
Tap a light bulb to turn it on or off. Watch the number and letter change.
Turn a word into binary
Codebreaker tasks
Task 1: Decode this word.
00010 = 2 and 00101 = 4 + 1 = 5. What are the 2nd and 5th letters?
Task 2: Decode this word.
10011 = 16 + 2 + 1 = 19. Count 19 letters into the alphabet.
Task 3 (brain stretch): What is the biggest number you can make with 5 switches? Type the number.
All the switches are on. Add 16 + 8 + 4 + 2 + 1.
Quick quiz
Egyptian Hieroglyphs
Picture writing from ancient Egypt, over 5,000 years old.
How it works
Ancient Egyptian writers, called scribes, used little pictures called hieroglyphs. Some pictures stood for whole words, but many stood for sounds, just like our letters do.
For hundreds of years, nobody could read them. Then in 1822, a French scholar named Jean-François Champollion cracked the code using the Rosetta Stone, a rock with the same message carved in three kinds of writing.
Kings and queens wrote their names inside an oval called a cartouche to show they were royal.
Some sounds share a picture. C and K sound the same, so they both use the basket. F and V share the viper, and U and W share the baby quail.
The hieroglyph alphabet
Example: writing "CAT"
Basket (C) + vulture (A) + bread (T) = CAT. Egyptians loved cats!
Try it: make your royal cartouche
Type your name to see it written like a pharaoh's.
Codebreaker tasks
Task 1: Decode this word.
The first picture is a foot. Find the foot in the alphabet chart.
Task 2: Decode this word.
The owl is M. The lasso appears twice.
Task 3: Decode this word.
It starts with the folded cloth and ends with the mouth. It shines at night.
Quick quiz
Pigpen Cipher
Letters hidden inside tic-tac-toe boards and X's.
How it works
In the pigpen cipher, every letter is replaced by the shape of the pen it lives in. Letters are placed in two tic-tac-toe grids and two X shapes. The second grid and second X have a dot in each space.
To write a letter, draw only the lines around its space (and the dot, if it has one).
Fun fact: a secret club called the Freemasons used this cipher about 300 years ago. That's why it is sometimes called the Freemason's cipher.
The pigpen key
Example: writing "HI"
H sits in the bottom middle of grid one, so it gets lines on the top, left, and right. I is in the bottom right corner, so it only gets lines on the top and left.
Try it: pigpen writer
Type a message and watch it turn into pigpen shapes.
Codebreaker tasks
Task 1: Decode this word.
The middle letter has a dot, so it lives in grid two.
Task 2: Decode this word.
The middle shape is a wedge from the X with no dot. Which side of the X points that way?
Task 3: Decode this two-word message.
The box shape with all four sides is E. It shows up three times!
Quick quiz
Caesar Shift
Slide the alphabet over to scramble your words.
How it works
Over 2,000 years ago, the Roman leader Julius Caesar sent secret messages to his army. He moved every letter 3 spots forward in the alphabet. A became D, B became E, and so on.
When you reach the end, you wrap around to the start: X becomes A, Y becomes B, and Z becomes C.
To decode, you do the opposite: move each letter back the same number of spots.
The number of spots you move is called the key. Your friend needs to know the key to read your message.
Example: "CAT" with a shift of 3
Try it: the shifter
Top row is the real letter. Bottom row is the secret letter.
Codebreaker tasks
Task 1: This message uses a shift of 3. Decode it.
Move each letter back 3. K goes back to J, I, H.
Task 2: This one uses a shift of 1. Decode it.
Move each letter back just one spot. It's the name of our class!
Task 3: Shift of 3 again. Watch out for letters that wrap around!
C goes back 3: B, A, then wrap around to Z.
Quick quiz
Number Code
Every letter gets a number. A is 1 and Z is 26.
How it works
This is one of the simplest codes in the world. Swap each letter for its place in the alphabet. Put a dash between letters and a slash between words.
Codebreakers call this the A1Z26 cipher, because A = 1 and Z = 26.
Example
3 = C, 1 = A, 20 = T. Then 8 = H, 1 = A, 20 = T. The message is CAT HAT.
Try it: number machine
Type words to turn them into numbers, or type numbers (like 8-9) to turn them back into words.
Codebreaker tasks
Task 1: Decode this word.
13 is right in the middle of the alphabet.
Task 2: Decode this two-word message.
That's what you are becoming!
Task 3 (math challenge): Add up each word's numbers. Which word is worth more: DOG or CAT?
CAT = 3 + 1 + 20. Now do DOG = 4 + 15 + 7.
Quick quiz
Morse Code
Messages made of short beeps and long beeps.
How it works
In the 1830s and 1840s, Samuel Morse helped invent the telegraph, a machine that sent beeps through long wires. Each letter is a pattern of dots (short beeps) and dashes (long beeps).
Letters are separated by a space, and words are separated by a slash ( / ).
The most famous Morse message is SOS: ... --- ... Ships used it to call for help because it is easy to send and hard to mistake.
The Morse alphabet
Example: "HI"
Four dots is H. Two dots is I.
Try it: Morse beeper
Type a message to see it in Morse code, then press play to hear it.
Codebreaker tasks
Task 1: Decode this famous message.
Three dots, three dashes, three dots. Scroll up to the fun fact!
Task 2: Decode this word.
The last letter is just one dot. That's the most common letter in English: E.
Task 3 (listening challenge): Press play and listen. Write down short and long beeps, then decode the word.
It's a three-letter word. The last letter is dash-dot (N).
Quick quiz
The Big Test
Eight questions from every code. Get 7 or more right on your first try to earn the Test stamp.
Only your first answer counts, so think before you tap. You can use the charts on the other pages to help!
Solve the Mystery
Use every code you learned to crack the case.
The Case of the Golden Scarab
On Monday morning, the Golden Scarab, our class prize for the best codebreakers, was missing from Mr. Lehmkuhl's desk! All that was left was a folded note from a secret helper named Agent Ibis.
The suspects
Tap a suspect to cross them off when a clue rules them out.
The clues
Clue 1 (Binary): The person who took the Scarab has a pet ___.
Clue 2 (Morse Code): The person who took the Scarab always wears a ___.
Clue 3 (Pigpen): The person who took the Scarab does NOT wear ___.
Clue 4 (Caesar Shift, key of 3): Hiding place, word 1.
Clue 5 (Number Code): Hiding place, word 2.
Clue 6 (Hieroglyphs): Hiding place, word 3.
Detective notebook
Clues you crack show up here.
Final answer
Think it through! If your final answer is wrong, you must wait 5 minutes before you can try again. Real detectives check their clues first.