ACA Homophonic Cipher

Description

This cipher enciphers by substituting the letters of a 25 letter alphabet with two digit numbers. To encipher/decipher a table is prepared: The letters of the alphabet are written in a line. A four letter key is chosen. Starting with 01 below the first letter of the key, the first 25 numbers, are written in a line below. The other numbers are processed in the same manner. For the key THIS we obtain:
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
08
09
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
01
02
03
04
05
06
07
44
45
46
47
48
49
50
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
68
69
70
71
72
73
74
75
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
00
76
77
78
79
80
81
82
83
To encrypted a letter, a number found in the column indicated by the letter is chosen at random. For example, using the key THIS, the text "Enter the text" may be enciphered as: Beside the four letter key you may choose an 25 letter alphabet:

Note that CipherClerk enforced the use of a four letter key. For this reason, one can not proceed in the situation depicted above, unless the key is changed to four letters.

Mexican Army Cipher Disk

Basically the same cipher as described above, but it used two digits to encode all 26 letters of the alphabet. So for 21 letters there were 4 homophones, for the other 5 only 3.

To proceed, you may