Cryptology - Unofficial St. Mary's College of California Web Site

5.4. INTERRUPTED KEYWORD CIPHERS 75
we first pull out the C column, followed by the E column, and then the G, L and
finally O columns. This gives
plaintext
ciphertext
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
C A I P U Z E F M S X G H N T Y L D K P Q O B J Q V
as the substitution alphabet.
Examples: Use a Keyword Transposed Cipher.
(1) Encipher monoalphabetic using the keyword SIMPLE.
The columns of the alphabet look like
S I M P L E
A B C D F G
H J K N O Q
R T U V W X
Y Z
Pulling the columns off in alphabetical order gives the ciphertext alphabet
plaintext
ciphertext
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
E G Q X I B J T Z L F O W M C K U P D N V S A H R Y
From here the enciphering should again be quick.
(2) Encipher cryptology using the keyword SECRET.
(3) Decipher QFKLQ SFNYR using the keyword HOMOPHONE.
(4) Decipher RMHRF YFMFY BI using the keyword DIRECT. 4
⋄ ⋄ ⋄ ⋄ ⋄ ⋄ ⋄ ⋄ ⋄ ⋄ ⋄ ⋄
5.4 Interrupted Keyword Ciphers
In an Interrupted Keyword Cipher instead of removing duplicated letters
put in * as a placeholder. This time COLLEGE becomes
C O L * E G *
A B D F H I J
K M N P Q R S
T U V W X Y Z
4 (1) WCMCE OKTEG INZQ, (2) JHQSU XFXBQ, (3) polyphonic, (4) substitution.