How does the rail fence cipher work?

The text is written diagonally across a set number of rows (rails) in a zig-zag, then read off row by row. It is a transposition cipher: the letters are rearranged rather than replaced.

Why must I use the same rail count to decrypt?

The rail count defines the exact zig-zag path. Decrypting with a different number of rails produces gibberish, so encoder and decoder must agree on it.

How many rails should I use?

Any number from 2 upward. More rails scramble short messages more, but the cipher remains weak — with only a handful of possible rail counts, it is trivially broken by trying each one. Use it for puzzles and learning, not real security.

Does it scramble spaces and punctuation?

Yes. Every character, including spaces, digits and punctuation, occupies a position in the zig-zag, so they are rearranged along with the letters. Keep them in your input or the decrypted text will not line up.

Is the rail fence cipher secure?

No. It is a historical hand cipher with a tiny key space (just the number of rails). It is easy to break by brute force and offers no real protection — treat it as an educational or recreational cipher only.

What is the difference between a transposition and a substitution cipher?

A transposition cipher like the rail fence rearranges the existing letters; a substitution cipher like Caesar or Vigenère replaces each letter with a different one. The rail fence keeps every letter but changes their order.

No — the cipher runs entirely in your browser and nothing is sent to a server.

Rail Fence Cipher Encoder & Decoder

The rail fence cipher is a classic transposition cipher dating to ancient times and popular in puzzles and intro-to-cryptography lessons. Your text is written in a zig-zag across a chosen number of rows, or rails, then read off one row at a time, so the letters are rearranged rather than substituted. Choose encrypt or decrypt, set the rail count, and type — output updates instantly in your browser.

How it works

To encrypt, the tool walks down and up the rails in a zig-zag. Starting on rail 0 moving down, each character is placed on the current rail; when it reaches the bottom rail it bounces back up, and when it reaches the top it bounces down. After all characters are placed, the rails are concatenated top to bottom to form the cipher text.

To decrypt, the same zig-zag path is reconstructed to count how many characters land on each rail. The cipher text is then sliced into those rail strings, and the original order is rebuilt by walking the zig-zag again and pulling the next character from the appropriate rail. Because the path is fully determined by the rail count, both sides must use the same number of rails or the result is gibberish.

Example

Encrypt WEAREDISCOVERED with 3 rails. The zig-zag layout is:

W . . . E . . . C . . . R . .
. E . R . D . S . O . E . E .
. . A . . . I . . . V . . . D

Reading each row left to right gives rail 1 = WECR, rail 2 = ERDSOEE, rail 3 = AIVD. Concatenated, the cipher text is WECRERDSOEEAIVD. Decrypting that same string with 3 rails restores WEAREDISCOVERED.

Rails	Effect
2	Splits text into odd and even positions
3	Common classic setting (example above)
4+	More rows, slightly more scrambling

Nothing you type is uploaded — the cipher runs entirely in your browser.