Manual for the Solution of Military Ciphers

by Parker Hitt

Data for the Solution of Ciphers in Spanish

The Spanish language is written with the following alphabet:

A B C CH D E F G H I J L LL
M N Ñ O P Q R RR S T U V X Y Z

while the exact sense often depends upon the use of accents over the vowels. However, in cipher work it is exceedingly inconvenient to use the permanent digraphs, CH, LL and RR and they do not appear as such in any specimens of Spanish or Mexican cipher examined. Accented vowels and Ñ are also not found and we may, in general, say that a cipher whose text is Spanish will be prepared with the following alphabet:

A B C D E F G H I J L M N O P Q R S T U V X Y Z

and the receiver must supply the accents and the tilde over the N to conform to the general sense.

However, many Mexican cipher alphabets contain the letters K and W. This is particularly true of the ciphers in use by secret service agents who must be prepared to handle words like NEW YORK, WILSON and WASHINGTON. The letters K and W will, however, have a negligible frequency except in short messages where words like these occur more than once.

In this connection, if a cipher contains Mexican geographical names like CHIHUAHUA, MEXICO, MUZQUIZ, the letters H, X and Z will have a somewhat exaggerated frequency.

In Spanish, the letter Q is always followed by U and the U is always followed by one of the other vowels, A, E, I or O. As QUE or QUI occurs not infrequently in Spanish text, particularly in telegraphic correspondence, it is well worth noting that, if a Q occurs in a transposition cipher, we must connect it with U and another vowel. The clue to several transposition ciphers has been found from this simple relation.

Table VII.—Normal frequency table for military orders and reports, calculated on a basis of 10,000 letters of Spanish text. The graphic form is on a basis of 200 letters.

	10,000 Letters	200 Letters
A	1352	27	111111111111111111111111111
B	102	2	11
C	474	9	111111111
D	524	10	1111111111
E	1402	28	1111111111111111111111111111
F	91	2	11
G	137	3	111
H	102	2	11
I	606	12	111111111111
J	41	1	1
L	517	10	1111111111
M	300	6	111111
N	619	12	111111111111
O	818	16	1111111111111111
P	257	5	11111
Q	87	2	11
R	751	15	111111111111111
S	724	14	11111111111111
T	422	8	11111111
U	387	7	1111111
V	85	2	11
X	6
Y	103	2	11
Z	42	1	1

In this table the vowels AEIOU = 45.65%; consonants LNRST = 30.33%; consonants JKQXZ = 1.76%.

Order of letters:

E A O R S N I D L C T U M P G Y (BH) F Q V Z J X.

Table VIII.—Table of frequency of digraphs, duals or pairs, Spanish text. Like Table III, this table is on the basis of 2,000 letters although prepared from a count of 20,000 letters. For this reason it is, to a certain extent an approximation; that is, merely because no figures are shown for certain combinations, we should not assume that such combinations never occur but rather that they are rare. The letters in the horizontal lines at the top and bottom are the leading letters; those in the vertical columns at the sides are the following letters. Thus, in two thousand letters, we may expect to find AI twice and IA twenty-three times.

	A	B	C	D	E	F	G	H	I	J	L	M	N	O	P	Q	R	S	T	U	V	X	Y	Z
A	9	4	19	11	5		6	17	23		54	18	9	3	20		29	11	21	8	6		2	5	A
B	6								3			1		4											B
C	24		6	6	24				5		3		8	8			9	5		2			2		C
D	31				29				3				19	13			10	9					4		D
E	12	2	6	59	10		1	5	7	2	12	18	22	4	9		38	25	28	25	3		3		E
F	4				4						4		3					3					1		F
G	2				4				8				4											2	G
H	2		12		10													2					1		H
I	2		23	16		5	2				3	11	13				6	10	5		3				I
J	3				2								1												J
L	21	3	6		39	3	3		7		21		5	6			12	2		2					L
M	12				6				5		1		6	15			7	2		6			1		M
N	32				46		2		8					32						12			2		N
O			26	22	2	6	3	4	9		16	2	8		20		15	7	11						O
P	13				3				2		4	9	2	7			4	11							P
Q	11	5									1		2				3		1						Q
R	40				27	2			4		4			36	3		11		17	3					R
S	39				52				10				7	14			2			14			3		S
T	5				13				4		4		18	5			6	30							T
U	2		4	2	6	3	4			5		2	6		4	17		15	2				1		U
V	2				2						2			2				2					2		V
X																									X
Y	5				6									2				5		2				2	Y
Z	1				2								1				4			2					Z
	A	B	C	D	E	F	G	H	I	J	L	M	N	O	P	Q	R	S	T	U	V	X	Y	Z

Table IX.—Order of frequency of common pairs to be expected in a count of 2,000 letters of Spanish military orders and reports. Based on Table VIII.

DE	59	ON	32	AC	24
LA	54	AD	31	EC	24
ES	52	ST	30	CI	23
EN	46	ED	29	IA	23
AR	40	RA	29	DO	22
AS	39	TE	28	NE	22
EL	39	ER	27	AL	21
RE	38	CO	26	LL	21
OR	36	SE	25	PA	20
AN	32	UE	25	PO	20

Alphabetic Frequency Tables

(Truesdell)

Frequency of occurrence in 1,000 letters of text:

Letter	French	German	Italian	Portuguese
A	80	52	117	140
B	6	18	6	6
C	33	31	45	34
D	40	51	31	40
E	197	173	126	142
F	9	21	10	12
G	7	42	17	10
H	6	41	6	10
I	65	81	114	59
J	3	1	[1]	5
K	[1]	10	[1]
L	49	28	72	32
M	31	20	30	46
N	79	120	66	48
O	57	28	93	110
P	32	8	30	28
Q	12	[1]	3	16
R	74	69	64	64
S	66	57	49	88
T	65	60	60	43
U	62	51	29	46
V	21	9	20	15
W	[1]	15
X	3	[1]	[1]	1
Y	2	[1]	[1]	1
Z	1	14	12	4