Bazeries Cipher

Question 1

How to encrypt using Bazeries cipher

Answer

Bazeries encryption uses a number N, and two identical grids (usually square grids of 25 distinct characters). Bazeries suggested generating the second grid from the number N written in letters, but any keyword is fine too.

Example: To crypt DCODE with N=23, use a first grid, generated with the alphabet (without J) and written in columns:

\	1	2	3	4	5
1	A	F	L	Q	V
2	B	G	M	R	W
3	C	H	N	S	X
4	D	I	O	T	Y
5	E	K	P	U	Z

Example: And the second grid generated with the keyword TWENTYTHREE (one could have took TWOTHREE)

\	1	2	3	4	5
1	T	W	E	N	Y
2	H	R	A	B	C
3	D	F	G	I	K
4	L	M	O	P	Q
5	S	U	V	X	Z

The message is segmented by groups of letters with cardinality equals to each digit of N (repeated if necessary).

Example: The number 23 is made of the digits 2 and 3, so split in 2 then 3 letters: DC then ODE.

The groups are then written backward

Example: DC becomes CD and ODE becomes EDO

The letters are located in the grid 1 and replaced by the letter in the same position in grid 2.

Example: C (line 3, column 1, grid 1) is replaced by D (line 3, column 1, grid 1) and so on.

Example: The final Bazeries ciphered message is DLSLO

Question 2

How to decrypt Bazeries cipher

Answer

Bazeries decryption requires a number N and two grids (or the keys to generate them).

Example: The cipher message is DLSLO, the number N=23, grid 1 transposed (without key) is :

\	1	2	3	4	5
1	A	F	L	Q	V
2	B	G	M	R	W
3	C	H	N	S	X
4	D	I	O	T	Y
5	E	K	P	U	Z

and grid 2 (key : TWENTYTHREE created from N) :

\	1	2	3	4	5
1	T	W	E	N	Y
2	H	R	A	B	C
3	D	F	G	I	K
4	L	M	O	P	Q
5	S	U	V	X	Z

The message is segmented by groups of letters with cardinality equals to each digit of N (repeated if necessary).

Example: 23 is made of the digits 2 and 3, let's split the message by 2 then 3 letters: DL and SLO.

Groups of letters are written backward

Example: DL becomes LD and SLO becomes OLS

Each letter is located in the second grid, and replaced by the letter with the same coordinate in the first grid.

Example: L (line 4, column 1, grid 2) is replaced by D (line 4, column 1, grid 1) and so on.

Example: The original plain text is DCODE.

Question 3

How to recognize a Bazeries ciphertext?

Answer

A Bazeries ciphered message has an index of coincidence close to the language of the plain text.

Question 4

How to decipher Bazeries without key?

Answer

One can crack Bazeries using frequency analysis, as it is a substitution, but a manual analysis is then needed to find the key used and reverse segments of the message.

Question 5

What are the variants of the Bazeries cipher?

Answer

Grids can be written in rows or in columns, they also can be switched.

Bazeries is already considered a variant of the Polybius cipher.

Question 6

When Bazeries have been invented ?

Answer

Etienne Bazeries would have created this cipher near 1980.

Bazeries Cipher

Bazeries Decoder

Bazeries Encoder

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