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Book Cipher

Numbers pointing at words in a book you both own. Nothing to break, because the key is on your shelf.

Rail Fence

Press Run it to start the machine.
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Result —

How it works

The story

Crack these

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Take it off the screen

Print this page and you get a worksheet: how the cipher works, where it came from, and the puzzles to crack, with the machine and the menus left off.

Print this page as a worksheet Try the challenges

Read more elsewhere

Longer, harder and written for grown-ups. Worth a look when this page runs out.

Book cipher