Beaufort

The Beaufort cipher is a variation upon the Vigenère cipher. I recommend that you are familiar with Vigenère before continuing with this.

Beaufort uses the same tableau as Vigenère.

A B C D E F G H I J K L M N O P Q R S T U V W X Y Z
B C D E F G H I J K L M N O P Q R S T U V W X Y Z A
C D E F G H I J K L M N O P Q R S T U V W X Y Z A B
D E F G H I J K L M N O P Q R S T U V W X Y Z A B C
E F G H I J K L M N O P Q R S T U V W X Y Z A B C D
F G H I J K L M N O P Q R S T U V W X Y Z A B C D E
G H I J K L M N O P Q R S T U V W X Y Z A B C D E F
H I J K L M N O P Q R S T U V W X Y Z A B C D E F G
I J K L M N O P Q R S T U V W X Y Z A B C D E F G H
J K L M N O P Q R S T U V W X Y Z A B C D E F G H I
K L M N O P Q R S T U V W X Y Z A B C D E F G H I J
L M N O P Q R S T U V W X Y Z A B C D E F G H I J K
M N O P Q R S T U V W X Y Z A B C D E F G H I J K L
N O P Q R S T U V W X Y Z A B C D E F G H I J K L M
O P Q R S T U V W X Y Z A B C D E F G H I J K L M N
P Q R S T U V W X Y Z A B C D E F G H I J K L M N O
Q R S T U V W X Y Z A B C D E F G H I J K L M N O P
R S T U V W X Y Z A B C D E F G H I J K L M N O P S
S T U V W X Y Z A B C D E F G H I J K L M N O P Q R
T U V W X Y Z A B C D E F G H I J K L M N O P Q R S
U V W X Y Z A B C D E F G H I J K L M N O P Q R S T
V W X Y Z A B C D E F G H I J K L M N O P Q R S T U
W X Y Z A B C D E F G H I J K L M N O P Q R S T U V
X Y Z A B C D E F G H I J K L M N O P Q R S T U V W
Y Z A B C D E F G H I J K L M N O P Q R S T U V W X
Z A B C D E F G H I J K L M N O P Q R S T U V W X Y

The Vigenè uses this cipher by having plaintext on one edge, key on the other, reading down and across to find the ciphertext. This has the disadvantage of making decoding a different operation to coding, one must start from one edge with the key letter, read along to find the ciphertext, then read up to find the plaintext. This can cause confusion.

Beaufort operates slightly differently. One starts on the edge with the letter to be encoded, reads along to find the key letter, then traces to the other edge to find the ciphertext.

Therefore, 'orange' encoded with 'lemons' will yield:

PT: ORANGE
KY: LEMONS
CT: XNMBHO

This method has the convenient effect that encoding and decoding are the same operation, this is quite convenient as only one operation needs to be learned. If we take 'XNMBHO' and encode it with 'LEMONS' we get 'ORANGE'!

The beaufort is no stronger or weaker than vigenère, and the method to crack it is the same.

Vigenere MugsVigenère and Beaufort mugs are available.

A series of posts which show how Beaufort can be analysed are elsewhere on this site.