buttcrack. Cipher Wiki

Rail fence

From the Buttcrack Cipher Wiki — the free field guide to classical ciphers

Rail fence — The message zigzags across a number of rails and is read off rail by rail.

Plaintext written along a zigzag of N rails, then read off rail by rail.

A worked example§

Encrypting a sample with the cipher itself, at build time:

MEET ME BY THE OLD CLOCK TOWER AT DAWN

Key: 3

produces the ciphertext

MMTLOOAWETEYHODLCTWRTANEBECKED

This example is generated by running the cipher when the page is built, and the round trip is checked, so it always matches what the solver does.

How it is broken§

The only unknowns are the rail count and the starting offset, so a few dozen readings cover every possibility.

History and context§

A Civil War field cipher on both sides, valued for needing no equipment beyond a stick to scratch lines in the dirt.

See also§

Columnar transposition · Skip / scytale · Route transposition · Myszkowski transposition · AMSCO transposition

Browse every cipher in the Transposition ciphers family, read the history of codebreaking, or return to the wiki main page.

Frequently asked questions§

How is the Rail fence broken?

The only unknowns are the rail count and the starting offset, so a few dozen readings cover every possibility.

What key does the Rail fence use?

rails + offset. The keyspace is unbounded in practice.

How much ciphertext do I need?

At least 8 characters for this solver to attempt it; short messages can be readable and still not be proof.

Can I break a Rail fence on this page?

Yes — the browser solver on this page handles it directly. Paste the ciphertext into the solver and press the button.

Categories: Transposition ciphers | Breakable in the browser | Cipher wiki
The facts in this article are generated from buttcrack's cipher registry when the site is built, so they describe the implementation you can run on this page. Registry-generated content is checked against the code; the history is editorial.

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It tries: Caesar, Atbash, ROT13, affine, Trithemius, rail fence, single-byte XOR, periodic Vigenère-family ciphers, autokey, selected encoding layers (such as Base64, hex, binary, decimal ASCII, Morse, and reverse), and—only with 60+ A–Z letters—statistical substitution.

It does not: prove a decryption, cover every classical cipher, or break modern encryption such as AES or RSA. Its ranking model is tuned for English, so a high score is a lead to verify with the method, key, and source context—not a guarantee.

Short text, non-English plaintext, non-Latin or symbol alphabets, missing keys, and unsupported formats can all leave no high-confidence answer. When that happens, the result includes input-specific observations and suggested next checks; those observations are not a claim to know the exact cause.

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