The Columnar Cipher is a classical transposition cipher that rearranges the letters of a plaintext message into columns and then reads them out in a permuted order according to a keyword. Unlike substitution ciphers, it obscures the message by reordering letters without changing them.
This cipher is closely related to other transposition methods such as the Columnar Transposition Cipher and the Grid Transposition Cipher, which also reorganize letters systematically to hide patterns in the plaintext.
Columnar Cipher: Encoding
To encode, write the plaintext beneath the keyword in rows, then read the letters column by column following the alphabetical order of the keyword letters. For example, using the keyword KEY and the message “CATENCODE”:
Plaintext: C A T E N C O D E
Keyword: K E Y
Arrange in rows beneath the keyword:
K E Y
C A T
E N C
O D E
Alphabetical order of keyword letters: E K Y
Read columns in order:
Column E → A N D
Column K → C E O
Column Y → T C E
Ciphertext: ANDCEOTCEColumnar Cipher: Decoding
Decoding reverses the process using the same keyword and column order. Place the letters back into columns according to the alphabetical order of the keyword, then read row by row:
Ciphertext: A N D C E O T C E
Keyword: K E Y
Alphabetical order: E K Y
Place letters into columns:
Column E → A N D
Column K → C E O
Column Y → T C E
Read row by row:
Row 1: C A T
Row 2: E N C
Row 3: O D E
Plaintext: CATENCODEColumnar Cipher: Notes
The Columnar Cipher demonstrates classical transposition principles. Writing plaintext under a keyword and reading columns in alphabetical order effectively hides patterns. This method underlies advanced techniques like the Columnar Transposition Cipher and the Cardan Grille Cipher, and matches modern Columnar Cipher tools like your Cipher Converter.