Appendix VII – Foursquare Cipher

c.t. Letter Frequencies (per 100 Digraphs)

a b c d e 5 6 7 8 4   a b c d e 5 6 8 8 4
f g h i k 3 2 5 4 3 f g h i k 3 2 4 5 3
l m n o p 4 4 4 8 6 l m n o p 5 4 4 7 5
q r s t u 3 3 5 8 6 q r s t u 3 3 5 9 6
v w x y z 1 0 0 1 1 v w x y z 1 0 1 2 2
5 6 6 7 5 a b c d e 4 6 7 6 5 a b c d e
3 3 5 4 2 f g h i k 1 1 4 5 2 f g h i k
5 3 3 9 5 l m n o p 4 3 3 9 5 l m n o p
4 3 5 6 8 q r s t u 4 2 6 7 6 q r s t u
1 0 0 1 1 v w x y z 1 1 0 3 1 v w x y z
 
Based upon 825,000 digraphs from English language word lists Based upon 5,000 digraphs: “Statistical Methods in Cryptanalysis” by Killback

JF78 AC-155 FOURSQUARE “U-Boating”

Sq 2: K S G M N X F R Y B V W L U E O P C T D Z H Q I A  
  16 14 13 12 10 10 10 9 9 7 7 7 6 6 5 5 5 4 4 3 3 2 2 1 170
 
Sq 4: C P Q F V L Y O X D S G N U W A I K R T W H M B Z  
  15 14 13 12 11 11 10 9 9 8 8 7 7 6 5 4 4 4 4 3 3 2 1 170

 

a b c d e D S R K U
f g h i k E O B L V
l m n o p P F C M X
q r s t u T W G N Y
v w x y z H A I Q Z
C D F N U a b c d e
R I G O W f g h i k
A V K P X l m n o p
S E L Q Y q r s t u
H B M T Z v w x y z