Rail Fence Cipher Tool

What is Rail Fence Cipher?

The Rail Fence Cipher is an ancient encryption technique based on arranging plaintext in a "rail" pattern, creating diagonal lines, and then reading characters row by row to produce ciphertext. This cipher uses one or more "rails" (or rows) to alter the arrangement of the plaintext, which scrambles its structure and increases the difficulty of decryption.

During encryption, the plaintext letters are distributed across multiple rows based on the number of rails. The ciphertext is formed by reading each row of characters in sequence. The more rails used, the more complex the encryption becomes. For decryption, you need to know the number of rails and the offset, then reverse the character arrangement to recover the original text.

How Does the Rail Fence Cipher Encrypt?

1. Determine the Number of Rails and Offset: Before encryption, you must first choose the number of rails (rows) and the offset (which row to start from).
2. Distribute the Plaintext Across the Rails: Characters from the plaintext are distributed across the specified number of rails, starting from the top rail and moving down, left to right, row by row.
3. Read Characters Row by Row: After distributing the plaintext, characters are read row by row to form the ciphertext.
4. Output the Ciphertext: The final ciphertext is the string obtained by reading the rows in sequence.

Example

If we use 3 rails to encrypt the plaintext "HELLO WORLD", the characters would be arranged as follows:

Reading row by row gives us the ciphertext: HOLELWRDLO.

How Does the Rail Fence Cipher Decrypt?

The decryption process is the reverse of encryption:

• Determine the Number of Rails and Offset: For decryption, you first need to know the number of rails and the offset used during encryption.
• Reconstruct the Rails: Using the length of the ciphertext and the number of rails, reconstruct the rail matrix. The offset will help determine the correct position for each character.
• Read Characters Column by Column: Finally, characters are read column by column to rebuild the original plaintext.

Example

If you know the ciphertext is "HOLELWRDLO", and the number of rails is 3 with an offset of 0, you would distribute the ciphertext into the rails as follows:

Reading column by column, you obtain the plaintext: HELLOWORLD。

How to Use the Rail Fence Cipher Tool?

1. Choose the Number of Rails and Offset: In the tool, you can set the number of rails (rows) and the offset (the starting row). These settings determine the encryption and decryption results.
2. Enter Plaintext or Ciphertext: Enter plaintext or ciphertext in the corresponding text box, and the tool will automatically complete encryption or decryption based on the set parameters.
3. Set Unrecognized Character Handling: During encryption and decryption, you can choose whether to keep unrecognized characters (such as spaces and punctuation). If "Ignore Unknown Characters" is selected, the system will skip non-alphabet characters, encrypting or decrypting only the letters.