Английская Википедия:Enigma rotor details
Шаблон:Multiple issues Шаблон:See also Шаблон:EnigmaSeries
This article contains technical details about the rotors of the Enigma machine. Understanding the way the machine encrypts requires taking into account the current position of each rotor, the ring setting and its internal wiring.
Physical design of rotors
| Exploded view of an Enigma rotor | Three rotors in sequence | ||
|---|---|---|---|
| Файл:Enigma rotor exploded view.png |
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Файл:Enigma rotor set.png | |
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The right side of a rotor, showing the pin electrical contacts. The Roman numeral V identifies the wiring of the rotor.
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The left side of an Enigma rotor, showing the flat (plate) electrical contacts. A single turnover notch is visible on the left edge of the rotor.
Rotor electrical view
No letter can map to itself, a cryptographic weakness caused by the same wires being used for forwards and backwards legs.
Rotor offset
The effect of rotation on the rotors can be demonstrated with some examples.
As an example, let us take rotor type I of Enigma I (see table below) without any ring setting offset. It can be seen that an Шаблон:Samp is encoded as an Шаблон:Samp, a Шаблон:Samp encoded as a Шаблон:Samp, and a Шаблон:Samp is encoded as an Шаблон:Samp. Notice that every letter is encoded into another.
In the case of the reflectors, in this example Wide Шаблон:Mono is taken (Reflector B in the table below) where an Шаблон:Mono is returned as a Шаблон:Mono and the Шаблон:Mono is returned as an Шаблон:Mono. Notice that the wirings are connected as a loop between two letters.
When a rotor has stepped, the offset must be taken into account to know what the output is, and where it enters the next rotor.
If for example rotor I is in the Шаблон:Mono-position, an Шаблон:Mono enters at the letter Шаблон:Mono which is wired to the Шаблон:Mono. Because of the offset this Шаблон:Mono enters the next rotor in the Шаблон:Mono position.
With the rotors I, II and III (from left to right), wide Шаблон:Mono, all ring settings in Шаблон:Mono, and start position Шаблон:Mono, typing Шаблон:Mono will produce the encoded sequence Шаблон:MonoШаблон:Citation needed.
Ring setting
The ring settings, or Ringstellung, are used to change the position of the alphabet ring relative to the internal wiring. Notch and alphabet ring are fixed together. Changing the ring setting will therefore change the positions of the wiring, relative to the turnover-point and start position.
The ring setting will rotate the wiring. Where rotor I in the Шаблон:Mono-position normally encodes an Шаблон:Mono into an Шаблон:Mono, with a ring setting offset Шаблон:Mono-02 it will be encoded into Шаблон:Mono
As mentioned before these encodings only happen after the key is pressed and the rotor has turned. Tracing the signal on the rotors Шаблон:Mono is therefore only possible if a key is pressed while the rotors were in the position Шаблон:Mono and the ring settings are all on Шаблон:Mono or Шаблон:Mono.
With the rotors I, II, III (from left to right), wide Шаблон:Mono, all ring settings in Шаблон:Mono, and start position Шаблон:Mono, typing Шаблон:Mono will produce the encoded sequence Шаблон:Mono.
Rotor wiring tables
This table shows how the internal wiring connects the right side of the rotor (with the spring-loaded contacts) to the left side. Each rotor is a simple substitution cipher. The letters are listed as connected to alphabet order. If the first letter of a rotor is Шаблон:Mono, this means that the Шаблон:Mono is wired to the Шаблон:Mono. This does not mean that Шаблон:Mono is wired to Шаблон:Mono; such looped wiring is only the case with the reflectors.
- Terminology
- The reflector is also known as the reversing drum or, from the German, the Umkehrwalze or UKW.
| Rotor # | Шаблон:Mono | Date Introduced | Model Name & Number |
|---|---|---|---|
| IC | Шаблон:Mono | 1924 | Commercial Enigma A, B |
| IIC | Шаблон:Mono | 1924 | Commercial Enigma A, B |
| IIIC | Шаблон:Mono | 1924 | Commercial Enigma A, B |
| Rotor # | Шаблон:Mono | Date Introduced | Model Name & Number |
| I | Шаблон:Mono | 7 February 1941 | German Railway (Rocket) |
| II | Шаблон:Mono | 7 February 1941 | German Railway (Rocket) |
| III | Шаблон:Mono | 7 February 1941 | German Railway (Rocket) |
| UKW | Шаблон:Mono | 7 February 1941 | German Railway (Rocket) |
| ETW | Шаблон:Mono | 7 February 1941 | German Railway (Rocket) |
| Rotor # | Шаблон:Mono | Date Introduced | Model Name & Number |
| I-K | Шаблон:Mono | February 1939 | Swiss K |
| II-K | Шаблон:Mono | February 1939 | Swiss K |
| III-K | Шаблон:Mono | February 1939 | Swiss K |
| UKW-K | Шаблон:Mono | February 1939 | Swiss K |
| ETW-K | Шаблон:Mono | February 1939 | Swiss K |
| Rotor # | Шаблон:Mono | Date Introduced | Model Name & Number |
| I | Шаблон:Mono | 1930 | Enigma I |
| II | Шаблон:Mono | 1930 | Enigma I |
| III | Шаблон:Mono | 1930 | Enigma I |
| IV | Шаблон:Mono | December 1938 | M3 Army |
| V | Шаблон:Mono | December 1938 | M3 Army |
| VI | Шаблон:Mono | 1939 | M3 & M4 Naval (FEB 1942) |
| VII | Шаблон:Mono | 1939 | M3 & M4 Naval (FEB 1942) |
| VIII | Шаблон:Mono | 1939 | M3 & M4 Naval (FEB 1942) |
| Rotor # | Шаблон:Mono | Date Introduced | Model Name & Number |
| Beta | Шаблон:Mono | Spring 1941 | M4 R2 |
| Gamma | Шаблон:Mono | Spring 1942 | M4 R2 |
| Reflector A | Шаблон:Mono | ||
| Reflector B | Шаблон:Mono | ||
| Reflector C | Шаблон:Mono | ||
| Reflector B Thin | Шаблон:Mono | 1940 | M4 R1 (M3 + Thin) |
| Reflector C Thin | Шаблон:Mono | 1940 | M4 R1 (M3 + Thin) |
| ETW | Шаблон:Mono | Enigma I |
Technical comments related to Enigma modifications 1939-1945.
Swiss K
In 1941 it became known to the Swiss that some of their Enigma traffic was being read by the French. It was decided to make some design modifications.
- One of the modifications consisted in modifying the wheel stepping on the Swiss Army machine. The slow, left-hand wheel was made stationary during operation while the second wheel stepped with every key stroke.
- The third wheel and the UKW would step in the normal fashion with Enigma stepping for the third wheel.
- The stationary but rotatable left-hand wheel was meant to make up for the missing stecker connections on the commercial machine.
Swiss Army Enigma machines were the only machines modified. The surviving Swiss Air Force machines do not show any signs of modification. Machines used by the diplomatic service apparently were not altered either.
Turnover notch positions
The single turnover notch positioned on the left side (plate connector side) of the rotor triggers the stepping motion by engaging the ratchet teeth of the wheel to the left. Later rotors had two turnover notches. The table below lists the turnover notch point of each rotor.
| Rotor | Notch | Effect |
|---|---|---|
| I | Q | If rotor steps from Q to R, the next rotor is advanced |
| II | E | If rotor steps from E to F, the next rotor is advanced |
| III | V | If rotor steps from V to W, the next rotor is advanced |
| IV | J | If rotor steps from J to K, the next rotor is advanced |
| V | Z | If rotor steps from Z to A, the next rotor is advanced |
| VI, VII, VIII | Z+M | If rotor steps from Z to A, or from M to N the next rotor is advanced |
Normalized Enigma sequences
In the following examples you can observe a normal step sequence and a double step sequence. The used rotors are (from left to right) I, II, III, with turnovers on Шаблон:Mono, Шаблон:Mono and Шаблон:Mono. It is the right rotor's behavior we observe here (turnover Шаблон:Mono).
- Normal sequence:
- Шаблон:Mono — normal step of right rotor
- Шаблон:Mono — right rotor (III) goes in V—notch position
- Шаблон:Mono — right rotor takes middle rotor one step further
- Шаблон:Mono — normal step of right rotor
- Double step sequence:
- Шаблон:Mono — normal step of right rotor
- Шаблон:Mono — right rotor (III) goes in V—notch position
- Шаблон:Mono — right rotor steps, takes middle rotor (II) one step further, which is now in its own E—notch position
- Шаблон:Mono — normal step of right rotor, double step of middle rotor, normal step of left rotor
- Шаблон:Mono — normal step of right rotor
Fourth rotor
The introduction of the fourth rotor was anticipated because captured material dated January 1941 had made reference to the development of a fourth rotor wheel;[2] indeed, the wiring of the new fourth rotor had already been worked out.
On 1 February 1942, the Enigma messages began to be encoded using a new Enigma version that had been brought into use. The previous 3-rotor Enigma model had been modified with the old reflector replaced by a thin rotor and a new thin reflector. Breaking Shark on 3-rotor bombes would have taken 50 to 100 times as long as an average Air Force or Army message. It seemed, therefore, that effective, fast, 4-rotor bombes were the only way forward. Encoding mistakes by cipher clerks allowed the British to determine the wiring of the new reflector and its rotor.[2]
References
External links
