From the Riddles of Ancient Egypt to Cryptography in the Renaissance — 3500 Years in the Making - Codes: The Guide to Secrecy from Ancient to Modern Times - page 51

continue our journey. Given below is the Trithemius tableau where all possible
shifts (modulo 24) appear as rows below the plaintext, each row representing
a distinct cipher alphabet (key), a total of 24 cipher alphabets (keys) in all,
polyalphabeticity! Trithemius used 24 letters, excluding the letters j and v .
The Trithimius Tableau
a b c d e f g h i k l m n o p q r s t u w x y z
a A B C D E F G H I K L M N O P Q R S T U W X Y Z
b B C D E F G H I K L M N O P Q R S T U W X Y Z A
c C D E F G H I K L M N O P Q R S T U W X Y Z A B
d D E F G H I K L M N O P Q R S T U W X Y Z A B C
e E F G H I K L M N O P Q R S T U W X Y Z A B C D
f F G H I K L M N O P Q R S T U W X Y Z A B C D E
g G H I K L M N O P Q R S T U W X Y Z A B C D E F
h H I K L M N O P Q R S T U W X Y Z A B C D E F G
i I K L M N O P Q R S T U W X Y Z A B C D E F G H
k K L M N O P Q R S T U W X Y Z A B C D E F G H I
l L M N O P Q R S T U W X Y Z A B C D E F G H I K
m M N O P Q R S T U W X Y Z A B C D E F G H I K L
n N O P Q R S T U W X Y Z A B C D E F G H I K L M
o O P Q R S T U W X Y Z A B C D E F G H I K L M N
p P Q R S T U W X Y Z A B C D E F G H I K L M N O
q Q R S T U W X Y Z A B C D E F G H I K L M N O P
r R S T U W X Y Z A B C D E F G H I K L M N O P Q
s S T U W X Y Z A B C D E F G H I K L M N O P Q R
t T U W X Y Z A B C D E F G H I K L M N O P Q R S
u U W X Y Z A B C D E F G H I K L M N O P Q R S T
w W X Y Z A B C D E F G H I K L M N O P Q R S T U
x X Y Z A B C D E F G H I K L M N O P Q R S T U W
y Y Z A B C D E F G H I K L M N O P Q R S T U W X
z Z A B C D E F G H I K L M N O P Q R S T U W X Y
To illustrate its use, we suppose that the plaintext is maximilian , then the
ciphertext is achieved by looking at the first row for the first letter under the
letter m , which is M , then for the second letter a of the plaintext look at the
letter below it in the second row, which is B , for the third letter of the plaintext
x , look at the letter below it in the third row, Z , and so on to get the ciphertext
MBZMQORQIX . If we have plaintext that is longer than 24 letters, then we can
start over again in the first row and repeat the process, (mod 24 arithmetic in
action). Notice that unlike a simple mono alphabetic substitution cipher, such
as the Caesar cipher, having only one cipher alphabet — the row below the
plaintext — a given plaintext in a polyalphabetic letter does not always go to
the same ciphertext letter. For instance, in our plaintext, the letter i goes to
M in the first instance, O in the second instance, and Q in the third instance,
since i sits in the fourth, sixth, and eighth places of the plaintext corresponding
to the fourth, sixth, and eighth row entries of ciphertext (in other words in the
corresponding cipher alphabet determined by that row) sitting below i , namely,