Rail Fence Cipher Decoder

Rail Fence Cipher Explained

The Rail Fence Cipher is a classic transposition cipher that encodes text by arranging it in a zigzag pattern across multiple "rails" (rows) and then reading it off row by row. This method effectively obscures the order of the characters, making the ciphertext harder to decipher without the key.

How It Works

1. Arrangement in Rails:

   Write the plaintext in a zigzag pattern down and up across a specified number of rails.

   Example: For 3 rails, the text "WE ARE DISCOVERED FLEE AT ONCE" is arranged like this:

   Layout

   W . . . . . . R . . . . . . I . . . . . . V . . . . . . . . . D

   
   

   . . E . T . C . E . A . E . D . S . O . E . E . L . E . .

   
   

   . . A . . N . . E . . C . . R . . F . . O

2. Reading Off:

   Read the text row by row to obtain the ciphertext.

   Ciphertext: From the arrangement above, the result would be "WRIVDETCEAEDSOEE LEA NE CRF O".

Decryption Process

1. Reconstruct the Rails:

   Determine the zigzag pattern for the given number of rails and place the ciphertext characters into the correct positions on the rails.

   Reconstruct the plaintext by reading characters in the zigzag pattern.

2. Example:

   Given the ciphertext "WRIVDETCEAEDSOEE LEA NE CRF O" and 3 rails, reconstruct the rails and then read off to get back to "WE ARE DISCOVERED FLEE AT ONCE".

Key Points

• Number of Rails: The number of rails determines the complexity of the cipher. More rails provide greater obfuscation.
• Simple Implementation: The Rail Fence Cipher is easy to implement and understand but provides a basic level of security.

This method is named after the way the text is written in a zigzag pattern resembling a fence. It’s an example of a transposition cipher, where the positions of the characters are permuted to hide the message.