Lewis Carroll, who wrote Alice’s Adventures in Wonderland, published this cipher on a card in 1868. The table holds 26 alphabets, each one shifted along by a step. Write your key word over the message; the key letter picks the column, the message letter picks the row, and where they cross is your cipher letter.
The cipher Alice’s author thought was unbreakable
Lewis Carroll, who wrote Alice’s Adventures in Wonderland, was a mathematician at Oxford. He published this table anonymously on a single card and claimed nobody could read a message without the key word. He was slightly wrong: Charles Babbage and a Prussian officer named Kasiski had already found a way in, by spotting how often the key word repeats. It is still a very good cipher.
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 Its sheet in the pack Try the challengesLonger, harder and written for grown-ups. Worth a look when this page runs out.