What you need
The printed table and pad, two copies of each
A pencil
A friend who has the matching copy
Somewhere to burn or shred the used pages
How to build it
Print two copies of both sheetsOne set for you, one for your friend. The pad must be identical or nothing works.
Pick a starting group and say where it isSend the first five letters of the pad in the clear. That tells your friend where to start and nothing else.
Write the key letters under your messageOne key letter under each message letter, straight off the pad, in order.
Find each letter in the tableMessage letter across the top, key letter down the side. The letter where they meet is your cipher letter.
Send only the cipher lettersNever the pad, never the starting position twice.
Cross the used groups outThen destroy the page. A pad used twice is worse than no cipher at all.
This pad is printed in a book, so it is not secret. Anybody with this page can read anything you send with it. It is here to practise on. A real pad has to be random, made by you, and it has to exist in exactly two copies.
The template
Print this at 100 per cent, not fit to page, or the sizes will be wrong. The ruler line below tells you whether it printed correctly.
The bar above should measure exactly 10 centimetres. If it does not, your printer has shrunk the page.
Now send something
Send MEET ME AT NOON. Then decode your friend’s reply using exactly the same steps, because the table works both ways round.
Why it cannot be brokenBack to MakeRead more elsewhere
Longer, harder and written for grown-ups. Worth a look when this page runs out.