Cipher Decoders

Paste the code, set the key, and watch a classical cipher come apart one step at a time.

These pages undo classical ciphers, the pen-and-paper kind from puzzle hunts, escape rooms and history lessons. Each decodes and encodes one cipher with its working on show, so a wrong key fails where you can see it.

7 pages

Ciphers that replace letters or words 4

The message is swapped for numbers or for other letters. Trifid is filed here although it also shuffles, because the swap comes first.

Book Cipher DecoderDecodes and encodes book cipher numbers against any text you paste, in 15 formats from a plain word count to page, line, word and letter. the key is under the owl
Vernam Cipher DecoderDecodes and encodes a Vernam cipher by letter values or by five-bit tape codes, with a step table, a random key maker and a look at what goes wrong when a key is used twice. SENDMOREBISCUITS
Trifid Cipher DecoderDecodes and encodes Delastelle's trifid cipher under any key and group size, with the three squares drawn, every digit shown, and a plus sign or # in the spare cell. LEAVETHETRIFLEINTHEFRIDGE
Jefferson Cipher DecoderDecodes and encodes the Jefferson wheel cipher on the 25 wheels of the US Army's M-94 or the ten wheels of Wikipedia's example, with all 25 rows on show. ASPAREKEYISUNDERTHEKETTLE

Ciphers that rearrange the letters 2

Every letter of the message is still there, only in the wrong order. Counting the letters is the first clue.

Scytale Cipher DecoderDecode or encode a scytale strip on a drawn rod, try every rod size in one table, and check your working against 27 worked codes. APENCILHASSIXSIDESWITHNOTHINGWRITTENONTHEM
Columnar Cipher DecoderDecodes and encodes columnar transposition under any key word, with short or padded last rows, a second key, and 20 spiral, snake and diagonal routes. NOBODYHASFEDTHEPIGEONSINCETUESDAY

To print and cut out 1

Paper tools for a table or a classroom, with no screen needed once they are printed.

Caesar Cipher Wheel PrintableA two-disc Caesar wheel on one A4 or Letter sheet, a four-level worksheet of 24 coded messages with an answer key, and a pigpen key card. meet me by the old oak tree

More about these tools

A book cipher swaps words for numbers that point into a text both sides own. A Vernam cipher adds a key one letter at a time, a trifid sends each letter through three squares, and a Jefferson cipher stacks lettered wheels. A scytale and a columnar transposition keep every letter and shuffle the order. The Caesar wheel prints on one sheet for a classroom. Under each tool is the table its cipher runs on. Keep real secrets out of all of them: most fall to a pencil and some patience, and a one-time pad only holds while its key is random, as long as the message, never reused and kept secret.

Ciphers that replace letters or words 4

Ciphers that rearrange the letters 2

To print and cut out 1

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