Rout Cipher

The Rout Cipher is a columnar transposition cipher that rearranges letters of a plaintext into a grid defined by a keyword. Letters are then read off column by column in alphabetical order of the keyword letters. Spaces are removed during encoding, and if the last row is incomplete, it may be padded to fill the grid. The recipient decodes by reconstructing the grid and reading row by row.

Its security relies entirely on the secrecy of the keyword. It does not substitute letters but only rearranges them.

Rout Cipher: Encoding

Example: Encode "catencode" with the keyword "key".

Plaintext: catencode Keyword: KEY (length 3)

Remove spaces and lowercase → catencode

Arrange letters into rows (columns = keyword length = 3):

c a t
e n c
o d e

Alphabetical order of keyword letters:
E → column 1
K → column 0
Y → column 2
→ Column read order: 1, 0, 2

Read columns in order:
Column 1 → a n d
Column 0 → c e o
Column 2 → t c e

Ciphertext: andceotce

Rout Cipher: Decoding

To decode, split the ciphertext into columns based on the keyword order, reconstruct the grid, then read row by row:

Ciphertext: andceotce Keyword: KEY

Columns (alphabetical keyword order):
E → column 1 → a n d
K → column 0 → c e o
Y → column 2 → t c e

Rebuild rows:
c a t
e n c
o d e

Row-wise reading → catencode

Rout Cipher: Notes

This version of the Rout Cipher demonstrates how transposition works with a keyword. The grid is reconstructed by the keyword's alphabetical order, making decoding possible only with the correct key. Padding ensures all columns are equal length, and spaces are ignored during encoding.