Computer Security and Cryptography

7.3 COMPONENTS OF THE RED MACHINE

The components of the RED machine include

1. A 60-contact half-rotor wired so that it enciphers vowels to vowels and consonants to consonants.

TABLE 7.2 Half-Rotor Substitution Table for θ

2. A plugboard connecting typewriter (input) to the rotor slip rings, where the typewriter keys for

(a) vowels A, E, I, O, U, and Y are connected to the six vowel slip rings, and

(b) consonants B, C, D, F,…, X, Z are connected to the 20 consonant slip rings.

3. A 47-position breakwheel, depicted in Figure 7.3, containing as many as 47 pins p₀, p₁, …, p₄₆, where the ith pin is either active p_i = 1, if present, or inactive p_i = 0, if missing.

The breakwheel (rotated) counterclockwise or stepped from the current active pin to the next active pin causes the counterclockwise rotation of the RED's half-rotor. Irregular stepping of the RED results from the removal of some pins, at least four and at most six. Only the 11 pins p₄, p₅, p₁₀, p₁₁, p₁₆, p₁₉, p₂₉, p₃₀, p₃₃, p₃₈, p₃₉ are removable. The rotor normally steps one position after the encipherment of a letter, but the breakwheel causes it to step k + 1 position if k consecutive pins are removed.

7.3.1 The Breakwheel and its Stepping Sequence

The rotor's position P(i) for the encipherment of plaintext letter x_i is an integer P(i) with 0 ≤ P(i) < 47; it depends on the initial position P(0) of the rotor and the locations ...