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