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Rail Fence (Zig-Zag) Cipher

Tools to decode/encode Rail Fence, a cipher using zig-zag writing, automatic decryption with brute-force mode.

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Rail Fence (Zig-Zag) Cipher -

Tag(s) : Transposition Cipher

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# Rail Fence (Zig-Zag) Cipher

## Rail Fence Decoder

### Parameters and Options

 Start from Top (left) from Bottom (left)

## Rail-Fence Encoder

 Start from Top (left) from Bottom (left)

### What is Rail Fence cipher? (Definition)

The Rail Fence cipher (also called zigzag) is a transposition cipher consisting in writing a text in zig-zag and reading it in a straight line.

### How to encrypt using Rail Fence cipher?

Rail Fence Encryption uses an integer for the number of levels of the zigzag.

The encoded message is written in zig-zag (like a rail fence/sawtooth) along a path with N levels/floors.

Example: Encrypt DCODEZIGZAG with N=3 is writing

 D---E---Z-- -C-D-Z-G-A- --O---I---G

The cipher message is read by rows.

Example: The encrypted message is DEZCDZGAOIG

### How to decrypt Rail Fence cipher?

RailFence decryption requires knowing the number of levels N.

Example: Decrypt the message DEZCDZGAOIG with N=3

Write the expected zigzag form and complete it by lines, before reading as zig zag

Example:

 X---X---X-- -X-X-X-X-X- --X---X---X
then
 D---E---Z-- -C-D-Z-G-A- --O---I---G

Example: The original plain text is DCODEZIGZAG.

### How to recognize Rail Fence ciphertext? (Identification)

A message encoded by Rail-Fence has an index of coincidence equal to that of the language of the original text.

Frequency analysis reveals usual occurrences of common letters similar to a plain text.

All references to zig-zag, sawtooth, up and down, path/track/route, etc. are clues.

Anything in the shape of bumps can also be a clue: camel, speed bump, etc.

The word rail can be the target of puns about trains, railroads, railway, cocaine/coke, etc.

### How to decipher Rail Fence without the number of levels?

Rail Fence can be cracked by testing all levels from 2 to N. Use the Brute-force attack button.

### What are the variants of the Rail Fence cipher?

There are several variations:

— The fence may begin with a peak or a hollow (up or down).

Example: A---E
-B-D-
--C--
(↘↗ hollow)

Example: --C--
-B-D-
A---E
(↗↘ peak)

— The first letter is not necessarily the base of the peak or hollow, the zig zag can start in the middle (equivalent to add spaces at the beginning)

Example: ----D-
-A-C-E
--B---
(One shift)

— It is possible to allow spaces and punctuation, which shifts the characters.

### What happens if the key is greater than or equal to the length of the text?

If the value of the number of levels is greater than or equal to the size of the text, then the text undergoes no encryption (no change).

### What is the difference between Rail Fence and ZigZag?

None, Rail Fence is the original word, ZigZag is the mnemonic term.

### When Rail-Fence was invented?

Rail-Fence is a basic transposition, no date or creator is recognized.

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Rail Fence (Zig-Zag) Cipher on dCode.fr [online website], retrieved on 2023-12-03, https://www.dcode.fr/rail-fence-cipher

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