Talk:Enigma rotor details

The ring setting does NOT rotate the internal wiring. This is always fixed and concealed in the cylindrical rotor body. The letter ring on the circumference of the rotor, on the other hand, can be adjusted in 26 positions relative to the internal wiring. If the letter ring, on which the notches were also located, had been firmly connected to the side of the output contacts, then any twisting would have exerted enormous forces on the internal wiring, to the point of tearing the cables off the contacts.

The ring setting does NOT rotate the internal wiring. This is always fixed and concealed in the cylindrical rotor body. The letter ring on the circumference of the rotor, on the other hand, can be adjusted in 26 positions relative to the internal wiring. If the letter ring, on which the notches were also located, had been firmly connected to the side of the output contacts, then any twisting would have exerted enormous forces on the internal wiring, to the point of tearing the cables off the contacts.

The adjustable letter or number bigram rings with the notches (1 to 9 notches per ring, depending on the Enigma model) had two main functions: 1. to mislead unauthorised persons (but ist had no influence on the key space of the basic positions: this is always identical to the length of the respective period length, regardless of how the letter rings are preset) and 2. to adjust the notch(es) relative to the internal wiring. In the rotors VI, VII and VIII of the Kriegsmarine, these (two!) notches were exactly opposite each other. This meant that there were only THIRTEEN different notch settings relative to the internal wiring. [[User:Permissiveactionlink|Permissiveactionlink]] ([[User talk:Permissiveactionlink|talk]]) 11:54, 4 July 2025 (UTC)

The adjustable letter or number bigram rings with the notches (1 to 9 notches per ring, depending on the Enigma model) had two main functions: 1. to mislead unauthorised persons (but ist had no influence on the key space of the basic positions: this is always identical to the length of the respective period length, regardless of how the letter rings are preset) and 2. to adjust the notch(es) relative to the internal wiring. In the rotors VI, VII and VIII of the Kriegsmarine, these (two!) notches were exactly opposite each other. This meant that there were only THIRTEEN different notch settings relative to the internal wiring. [[User:Permissiveactionlink|Permissiveactionlink]] ([[User talk:Permissiveactionlink|talk]]) 11:54, 4 July 2025 (UTC)

== Effect of the number of notches per rotor ==

Unfortunately, there is no reference in the article to the negative effects of the double stepping anomaly and a number of notches that is not relatively prime to the number of contacts Z of the rotors on the period length of the machine.

If the number of notches on a letter- or bigramring is relative prime to Z (1, 3, 5, 7, 9, 11, 15, 17, 19, 21, 23, 25), then the period length of the machine drops to 26*(26 - k)*26. k is the number of notches on the CENTRE rotor. Without the double stepping anomaly, the machine would have a period length of 17,576, if the middle rotor would have 25 notches. With the double stepping anomaly, the period length is reduced to 26*(26 - 25)*26 = 676. (!)

This changes completely if the number of notches is even or 13 (26 = 2*13, prime factorisation). Now the even number of notches on the right-hand rotor also has a negative effect, as does that on the centre rotor if its notch number is also even. The Marine Enigma M3 had five single-notch rotors and three two-notch rotors toi choose from. (X : any rotor, 1 : single-notch rotor, 2 : two-notch rotor). 120 rotor combinations were of type X-1-1, and had the "normal" period length of 26*25*26 = 16,900. 90 rotor combinations were of type X-1-2, each with a period length of 26*25*13 = 8,450. 90 rotor combinations were also of type X-2-1, but this time with a period length of 26*12*26 = 8,112. And there were only 36 different rotor combinations of type X-2-2, with a period length of only 26*12*13 = 4,056.

Two rotors with 13 notches each (X-13-13) would implode the period length to 26*1*2 = 52 (!)

The double stepping anomaly was NOT an unimportant design feature, it shorted the period length when using a higher number of notches (Enigma KD used 9-notched rotors : period length is shorted to 26*17*26 = 11,492 ciphering steps), and made cryptanalysis via "in depth" Analysis more possible with a lot of too long wireless encrypted messages. [[User:Permissiveactionlink|Permissiveactionlink]] ([[User talk:Permissiveactionlink|talk]]) 07:51, 7 July 2025 (UTC)