Bazeries

History

As well as independently inventing the cylinder cipher, which was originally invented by Thomas Jefferson, the Frenchman Commandant Étienne Bazeries also invented the Bazeries cipher which he described in his book Les Chiffres Secrets Dévoilés published in 1901.

Description

This cipher uses two 5x5 square grids; one filled with a straight alphabet and the other a keyed alphabet formed from a number. Plaintext letters are located in the first grid and the letter in the same position in the second grid is used as the cipher.

To encipher text using the Bazeries cipher two 5 x 5 square matrices are created and filled with different alphabets using all the letters of the alphabet, with J being replaced by I. If 6 x 6 square matrices are selected the 26 letters of the alphabet and numbers 0-9 are used with A followed by 1, B by 2, C by 3 and so on up to J followed by 0. The first alphabet is ordered A-Z and entered by columns into the first square. Next a number less than one million is selected and is spelled out in full.

For example the key number 7352 is written as SEVENTHOUSANDTHREEHUNDREDANDFIFTYTWO which becomes SEVNTHOUADRFIYW when repeated letters are removed. Appending unused alphabet letters produces the following keyed alphabet:

SEVNTHOUADRFIYWBCGJKLMPQXZ

This second keyed alphabet is written into the second square by rows.

To produce the cipher the plaintext is divided into groups determined by the key numbers and each group is reversed. The resulting text is enciphered by locating the plaintext letters in the left square and taking the letter from the second square in the same position.

A F L Q V | S E V N T
B G M R W | H O U A D

C H N S X | R F I Y W
D I O T Y | B C G K L

E K P U Z | M P Q X Z

Example

Key number: 7352 (SEVENTHOUSANDTHREEHUNDREDANDFIFTYTWO)

Plaintext: A clear conscience is usually the sign of a bad memory.

Plaintext: aclearc ons cienc ei susuall yth esign of abadmem ory

Reversed: craelca sno cneic ie llausus hty ngise fo memdaba yro

Ciphertext: RASMVRS YIG RIMCR CM VVSXYXY FKL IOCYM EG UMUBSHS LAG

Solving

Solving method: Brute force checking all keys up to 999,999.

Both 5x5 and 6x6 Bazeries solvers have been implemented.