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Rail Fence Cipher: Zigzag Encoder and Decoder

This free rail fence cipher tool writes your message in a zigzag across a number of rails and reads it off row by row. It encrypts, decrypts and shows the fence so you can see how it works.

By Debmedia Technologies LLP · Kolkata, India · Updated

What Is It and When Do You Need It?

The rail fence cipher scrambles a message by changing the order of its letters, not the letters themselves. The text is laid out in a wave pattern across a few rails and then read row by row. It is a favourite in puzzles because it is easy to do on paper.

Choose the number of rails, and the tool encrypts or decrypts, with a picture of the fence.

How to Use This Tool

  1. Type or paste your text.
  2. Choose the number of rails.
  3. Choose encrypt or decrypt.
  4. Press Run and read the result and the fence picture.

How the Calculation Works

The rail number of each character follows 0, 1, 2 … top, then back down … 1, 0 and so on. Encryption collects the characters of rail 0, then rail 1 and so on. Decryption works out how many characters belong to each rail, fills the rails in order and reads the zigzag again.

Worked Example

With 3 rails, WEAREDISCOVEREDFLEEATONCE becomes WECRLTEERDSOEEFEAOCAIVDEN.

Common Uses

  • Puzzles and escape rooms.
  • Teaching transposition.
  • Geocaching.
  • Studying classic ciphers.

Tips and Common Mistakes

  • Try 2, 3 and 4 rails when you do not know the key.
  • More rails make the text look more scrambled.
  • Spaces count as characters.

Next, you may need the Caesar cipher, Polybius square, Atbash cipher, Vigenère cipher.

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Frequently Asked Questions

The message is written diagonally down and up across several rows (the rails), like a zigzag. The cipher text is then read along each row from top to bottom.
No. It is a transposition cipher. The letters are the same, only their order changes.
Only the number of rails. Many puzzles try 2, 3, 4 and so on until the text reads normally.
Yes. Every character, including spaces, takes part in the zigzag. Remove spaces first if you want them out.

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