Code and ciphers: Julius Caesar, the Enigma and the internet

Table 10.6
The Hagelin cipher machine 151
Bar 26-Wheel 25-Wheel 23-Wheel 21-Wheel 19-Wheel 17-Wheel
1 X
2 X
3 X
4 X
5 X
6 X
7 X
8 X
9 X
10 X X
11 X X
12 X
13 X
14 X
15 X
16 X
17 X X
18 X X
19 X
20 X
21 X
22 X X
23 X X
24 X
25 X X
26 X X
27 X X
either one very long cipher message of several thousand letters,
or several messages of even greater total length.
He would then have to compute various statistics, beginning with an
overall frequency count of the cipher letters, which would help to establish
that a Hagelin machine was probably being used, for the nonuniform
distribution of the 26 possible key values would be detectable in
a sufficiently long text. If several texts had to be used it might be possible
to determine their ‘slides’ relative to each other by calculating their cipher
frequency correlation coefficients in pairs (if the machine was an M209,
with fixed slide, this wouldn’t arise).
The longest cipher text would now be written on a width of 17
columns and counts made of the cipher letters in each column. The
object here is to attempt to put each column into one of two classes: those