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A cipher you can hold beats a cipher on a screen. Card, string and a flashlight cover two thousand years of secret writing.

DIANA cryptosystem

A one-time pad you can really use: one table, no arithmetic, and it works both ways round.

A rod and a paper strip. The oldest code machine there is, and it takes five minutes.

Two card discs and a split pin. Turn it and the whole cipher changes.

The same build with a scrambled inner ring. Turn it mid-message and you have invented a harder cipher.

A card with windows cut in it, so a dull letter about the weather carries a secret.

Rotating grille

A six by six card that turns four times and fills every cell. Working out where to cut is the puzzle.

Jefferson wheel

Six rings of letters on a pencil, invented by a president and still in use a century later.

A length of cord and a marked strip. A message you can wear on your wrist.

Semaphore flags

Two dowels and two tea towels. Best used across a garden at a shouting distance.

Morse signal lamp

A torch, a code card in your pocket, and a friend at the end of the garden.

Lemon juice and a warm lamp. An adult holds the lamp, and never a flame.

Paper cone record player

A sewing needle, a paper cone and an old record. No electricity, and you will hear music come out of a scratch.

A comb, a cardboard tube and pins. Turn it and you have built a machine that remembers a tune.

Which one first?

Not in the order they are listed. In the order they work.

Start here, age 7

The scytale. A pencil, a paper strip, ten minutes, and no arithmetic. It is the only build where the key is an object rather than a word, and a child gets it immediately.

The Caesar wheel. Scissors and a split pin. This is the one they will use for weeks, because turning it changes the whole cipher.

For a dark evening

The signal lamp is five minutes and a torch, and it is the one that gets them outside and shouting across a garden.

The one nobody believes

The paper cone record player. A needle, paper, an old record, no electricity, and music comes out of a scratch.

What you will need across all of them

Almost nothing that is not already in a drawer.

Card, or cereal boxes

Scissors

Split pins, sometimes called paper fasteners

Sticky tape and glue

A pencil, and a rod of some kind

String or thin cord

A torch

A lemon

Four of the builds need an adult: anything with a craft knife, a pin, or heat. Each page says so at the point it matters, not buried at the top.

Before you print a template

Printers shrink pages unless you stop them. Set the scale to 100 per cent, not fit to page, or your two discs will not line up. Every template carries a ruler line so you can check before you cut anything.

Every build here also prints as a worksheet: the steps, the template and the safety note, with the menus left off.

The Make booklet The cipher sheets

Why build them at all

A cipher on a screen is a thing that happens to you. A cipher you have cut out of card is a thing you own, and the difference shows the moment it goes wrong: a jammed wheel, a strip that will not line up, a grille laid down back to front. Every one of those failures teaches the rule better than the animation does.

They also survive a flat battery, which is more than the rest of this site can say.