Secret codes for kids: easy codes to make at home, and why they matter

Few things excite a young child like a secret message. Codes are brilliant fun, and they also teach one of the big ideas behind computers: a symbol can stand for something else, as long as everyone knows the key. Here are secret codes for kids that you can make at the kitchen table, from picture codes to the code Julius Caesar is said to have used, how to crack them, and why codes turn up in Digital Technologies at school.

What is a secret code?

A code swaps information for symbols. The Australian Government’s Digital Technologies Hub explains that “Encoding a word or phrase is an example of representing data in a different way”, and that “Knowing the ‘key’ helps the decoder translate the message.” Writing and cracking codes even has its own name: “cryptography”.

The key is everything. KidStudy’s Secret Codes lesson sums it up for children: a code only works when both people share the key. Without it, the symbols are hard to read.

Codes are all around us

Before making secret codes, notice the everyday ones. A stop sign, the toilets sign and the recycling symbol all mean something without words. KidStudy’s grown-ups notes point out that children often think a symbol must look like the thing it stands for, but many symbols are simply agreed on, so we need to learn what they mean.

Go on a symbol hunt at home or on a walk: the play button on the TV remote, the warning sign on a cleaning product, the arrows on the recycling bin. Ask, “What does it tell us? How do we know?”

Five easy secret codes to make at home

1. A picture code with a key. Draw a symbol for each letter of your child’s name, such as a star for A. Write the name in symbols, then hand over the code and the key. In KidStudy’s lesson, a heart means H and a star means I, so heart, star spells “hi”.
2. The backwards alphabet code. Write the alphabet, then write it backwards underneath, so A becomes Z, B becomes Y, and so on. The Digital Technologies Hub lists it as one of “Two simple ways of encoding”.
3. The shifted alphabet code (Caesar shift). The other simple way is to slide the alphabet along. The Australian Association of Mathematics Teachers explains that Julius Caesar “is said to have” replaced “each letter in a message with the letter three places to the right in the alphabet”, so A becomes D, B becomes E and C becomes F. Make a code wheel from two paper circles joined in the middle with a split pin, and you can change the shift whenever you like.
4. A number code. Use 1 for A, 2 for B, 3 for C and so on. It’s a great one for practising the order of the alphabet, and it leads straight into binary codes, where computers turn those numbers into ones and zeros.
5. A tally code for counting. Tally marks are a code too. In KidStudy’s lesson, each line stands for one thing, and four lines with a line across makes five. Count the cars that go past, or the birds in the garden, in tallies.

Codes that use dots and flashes

Some codes aren’t secret at all: they’re built to help people communicate. The Digital Technologies Hub explains that “Morse code represents the letters of the alphabet using dots and dashes”, and that it “can be transmitted as symbols, sound or light”. Braille is “a system for representing text and other characters using combinations of flat and raised dots so they can be read by touch.” On paper, children can show a braille letter by drawing six small circles and colouring in the raised ones. Look for braille next time you’re in a lift or on public transport.

Why are codes part of Digital Technologies?

Computers store everything as symbols, so learning that a symbol stands for something, and that you need a key to read it, is a real Digital Technologies idea.

• In Victoria, children from Foundation to Level 2 learn to “explore patterns in data and represent data as objects, pictures, symbols, numbers and words” (VC2TDI2D01). The examples include “using a symbol to represent an idea, but knowing that the symbol is not the data itself”, and “recognising the equivalence of different representations of numbers, including words, digits and tally marks”. In Year 1 Maths, tally marks are one of the ways children record data (VC2M1ST01).
• In the Australian Curriculum, Years 1 and 2 children “represent data as pictures, symbols, numbers and words” (AC9TDI2K02).

Codes keep coming back. The Digital Technologies Hub has cipher lessons for Years 3 to 6, and Victoria’s Levels 5 and 6 include “converting letters in a message to numbers using their positions in the alphabet”. Real codes also keep us safe: the Australian Computing Academy notes that “We use secure ciphers (that are extremely hard to crack) to protect communication on the Internet”, such as card details when you shop online. Letters themselves are a kind of code for sounds, which is why our post on phonics at home fits nicely alongside code games.

KidStudy’s Year 2 Coding lesson, Secret Codes, covers symbols that stand for things (like stop, toilets and recycling signs), codes with a key, tally marks, and showing the same number as a word, tally marks and pictures. Its 10-minute home activity, Secret code message, has your child make a key with a symbol for each letter of their name, write their name in code, and see if you can crack it before you write a message back. For more screen-free ideas, see our post on unplugged coding activities.