Beaufort Code
We use a Vigenère method for the key, but change the method of resolving the ciphertext. For this we look along the top row for the plaintext letter, and then go down until we find the key, and then look along the row to the first column:
Plain 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 1 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 2 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 3 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 4 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 5 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 6 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 7 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 8 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 9 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 10 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 11 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 12 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 13 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 14 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 15 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 16 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 17 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 q 18 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 19 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 20 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 21 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 22 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 23 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 24 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 25 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
For example if we have a message of 'hello" and a key of 'bike', we first take h and 'b':
Start with char (h)-↓ Plain a b c d e f g h 1 - - - - - - - i 2 - - - - - - - j 3 - - - - - - - k 4 - - - - - - - l 5 - - - - - - - m 6 - - - - - - - n 7 - - - - - - - o 8 - - - - - - - p 9 - - - - - - - q 10 - - - - - - - r 11 - - - - - - - s 12 - - - - - - - t 13 - - - - - - - u 14 - - - - - - - v 15 - - - - - - - w 16 - - - - - - - x 17 - - - - - - - y 18 - - - - - - - z 19 - - - - - - - a 20 u←------------b ← Go down to key character (b)
Next we take 'e' and a key of 'i':
Char (e)------↓ Plain a b c d e 1 - - - - f 2 - - - - g 3 - - - - h 4 e←------i ← Go down to key character (i)
So that text of 'he' and a key of 'bi' will translate to a cipher text of 'ue'.