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

The Enigma cipher machine 113
Plate 9.1 One side of an Enigma wheel. The 26 spring contacts are on this side
and the smooth-notched setting ring surrounds the wheel itself. The machine
identification is M3564 and the wheel is identified as number 2 (in Roman
numerals).
be found in M14.) See Plates 9.1 and 9.2 for photographs of both sides of
an actual wheel from an Enigma machine.
The reflector was fixed in position and had 26 contacts on one side only.
Inside the reflector 13 wires connected the 26 contacts in pairs and so a
current entering one of the contact points of the reflector would exit at
another of the contact points. The internal wiring of the reflector was also
‘random’. Unlike the three wired wheels, the reflector was permanently
fixed in the machine and was only replaced once during the period
1930–45, in 1937.
The entry wheel provided the connection between the rightmost wheel
and the keyboard, and between the rightmost wheel and the lamps.
Somewhat surprisingly, the entry wheel was connected to the keyboard
letters in normal alphabetic order, rather than in keyboard order. This
gave no cryptographic advantage and must have involved some messy
internal wiring.
A simplified schematic diagram of the Enigma is shown in Figure 9.1.
The machine was housed in a wooden box. When the cover of the
machine was closed only the setting rings on the three movable wheels